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	$228.63	7.108%	$244.881	$244.88	$244.90	$244.90
Purchase #2	$165.53	5.422%	$174.505	$174.51	$174.50	$174.50
Purchase #3	$113.43	12.407%	$127.5033	$127.50	$127.50	$127.50
Purchase #4	$206.29	12.583%	$232.2475	$232.25	$232.25	$232.20
Purchase #5	$196.79	4.397%	$205.4429	$205.44	$205.45	$205.40
Purchase #6	$224.25	8.475%	$243.2552	$243.26	$243.25	$243.30
Purchase #7	$141.40	7.190%	$151.5667	$151.57	$151.55	$151.60
7 purchase totals =	$1,276.32		$1,379.4016	$1,379.41	$1,379.40	$1,379.40