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	$223.36	7.591%	$240.3153	$240.32	$240.30	$240.30
Purchase #2	$58.70	4.468%	$61.3227	$61.32	$61.30	$61.30
Purchase #3	$201.59	3.566%	$208.7787	$208.78	$208.80	$208.80
Purchase #4	$226.56	12.348%	$254.5356	$254.54	$254.55	$254.50
Purchase #5	$187.54	13.119%	$212.1434	$212.14	$212.15	$212.10
Purchase #6	$199.25	6.232%	$211.6673	$211.67	$211.65	$211.70
Purchase #7	$65.66	10.347%	$72.4538	$72.45	$72.45	$72.50
7 purchase totals =	$1,162.66		$1,261.2168	$1,261.22	$1,261.20	$1,261.20