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	$127.59	11.643%	$142.4453	$142.45	$142.45	$142.40
Purchase #2	$244.28	6.206%	$259.44	$259.44	$259.45	$259.40
Purchase #3	$94.44	9.797%	$103.6923	$103.69	$103.70	$103.70
Purchase #4	$98.41	13.362%	$111.5595	$111.56	$111.55	$111.60
Purchase #5	$87.32	5.258%	$91.9113	$91.91	$91.90	$91.90
Purchase #6	$174.54	7.201%	$187.1086	$187.11	$187.10	$187.10
Purchase #7	$124.74	3.695%	$129.3491	$129.35	$129.35	$129.30
7 purchase totals =	$951.32		$1,025.5061	$1,025.51	$1,025.50	$1,025.40