Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$145.99	11.281%	$162.4591	$162.46	$162.45	$162.50
Purchase #2	$89.37	13.790%	$101.6941	$101.69	$101.70	$101.70
Purchase #3	$241.63	5.271%	$254.3663	$254.37	$254.35	$254.40
Purchase #4	$198.73	8.256%	$215.1371	$215.14	$215.15	$215.10
Purchase #5	$137.32	10.427%	$151.6384	$151.64	$151.65	$151.60
Purchase #6	$201.37	10.517%	$222.5481	$222.55	$222.55	$222.50
Purchase #7	$243.43	10.853%	$269.8495	$269.85	$269.85	$269.80
7 purchase totals =	$1,257.84		$1,377.6926	$1,377.70	$1,377.70	$1,377.60