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	$205.86	4.258%	$214.6255	$214.63	$214.65	$214.60
Purchase #2	$74.79	4.372%	$78.0598	$78.06	$78.05	$78.10
Purchase #3	$129.42	9.292%	$141.4457	$141.45	$141.45	$141.40
Purchase #4	$158.76	12.448%	$178.5224	$178.52	$178.50	$178.50
Purchase #5	$106.93	11.452%	$119.1756	$119.18	$119.20	$119.20
Purchase #6	$71.40	10.483%	$78.8849	$78.88	$78.90	$78.90
Purchase #7	$81.33	8.675%	$88.3854	$88.39	$88.40	$88.40
7 purchase totals =	$828.49		$899.0993	$899.11	$899.15	$899.10