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	$55.87	6.159%	$59.311	$59.31	$59.30	$59.30
Purchase #2	$52.79	9.697%	$57.909	$57.91	$57.90	$57.90
Purchase #3	$225.26	3.286%	$232.662	$232.66	$232.65	$232.70
Purchase #4	$126.79	3.480%	$131.2023	$131.20	$131.20	$131.20
Purchase #5	$142.54	6.348%	$151.5884	$151.59	$151.60	$151.60
Purchase #6	$64.65	11.830%	$72.2981	$72.30	$72.30	$72.30
Purchase #7	$170.61	11.329%	$189.9384	$189.94	$189.95	$189.90
7 purchase totals =	$838.51		$894.9092	$894.91	$894.90	$894.90