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	$148.34	4.179%	$154.5391	$154.54	$154.55	$154.50
Purchase #2	$174.26	12.819%	$196.5984	$196.60	$196.60	$196.60
Purchase #3	$141.43	8.614%	$153.6128	$153.61	$153.60	$153.60
Purchase #4	$33.61	9.310%	$36.7391	$36.74	$36.75	$36.70
Purchase #5	$169.81	6.495%	$180.8392	$180.84	$180.85	$180.80
Purchase #6	$30.32	7.201%	$32.5033	$32.50	$32.50	$32.50
Purchase #7	$61.28	6.399%	$65.2013	$65.20	$65.20	$65.20
7 purchase totals =	$759.05		$820.0332	$820.03	$820.05	$819.90