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	$158.29	13.121%	$179.0592	$179.06	$179.05	$179.10
Purchase #2	$54.96	12.674%	$61.9256	$61.93	$61.95	$61.90
Purchase #3	$51.60	4.793%	$54.0732	$54.07	$54.05	$54.10
Purchase #4	$243.57	6.720%	$259.9379	$259.94	$259.95	$259.90
Purchase #5	$203.77	8.820%	$221.7425	$221.74	$221.75	$221.70
Purchase #6	$48.60	12.245%	$54.5511	$54.55	$54.55	$54.60
Purchase #7	$171.93	3.677%	$178.2519	$178.25	$178.25	$178.30
7 purchase totals =	$932.72		$1,009.5414	$1,009.54	$1,009.55	$1,009.60