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	$152.72	4.475%	$159.5542	$159.55	$159.55	$159.60
Purchase #2	$129.26	12.511%	$145.4317	$145.43	$145.45	$145.40
Purchase #3	$43.87	4.701%	$45.9323	$45.93	$45.95	$45.90
Purchase #4	$151.76	9.164%	$165.6673	$165.67	$165.65	$165.70
Purchase #5	$117.54	10.223%	$129.5561	$129.56	$129.55	$129.60
Purchase #6	$171.34	11.776%	$191.517	$191.52	$191.50	$191.50
Purchase #7	$154.27	3.206%	$159.2159	$159.22	$159.20	$159.20
7 purchase totals =	$920.76		$996.8745	$996.88	$996.85	$996.90