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	$32.48	8.503%	$35.2418	$35.24	$35.25	$35.20
Purchase #2	$182.31	3.619%	$188.9078	$188.91	$188.90	$188.90
Purchase #3	$172.67	5.811%	$182.7039	$182.70	$182.70	$182.70
Purchase #4	$113.41	9.187%	$123.829	$123.83	$123.85	$123.80
Purchase #5	$154.95	11.608%	$172.9366	$172.94	$172.95	$172.90
Purchase #6	$5.57	13.119%	$6.3007	$6.30	$6.30	$6.30
Purchase #7	$72.72	6.401%	$77.3748	$77.37	$77.35	$77.40
7 purchase totals =	$734.11		$787.2946	$787.29	$787.30	$787.20