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	$174.92	7.566%	$188.1544	$188.15	$188.15	$188.20
Purchase #2	$64.66	11.513%	$72.1043	$72.10	$72.10	$72.10
Purchase #3	$232.64	9.405%	$254.5198	$254.52	$254.50	$254.50
Purchase #4	$192.88	9.183%	$210.5922	$210.59	$210.60	$210.60
Purchase #5	$30.61	9.392%	$33.4849	$33.48	$33.50	$33.50
Purchase #6	$32.57	5.839%	$34.4718	$34.47	$34.45	$34.50
Purchase #7	$217.44	13.732%	$247.2989	$247.30	$247.30	$247.30
7 purchase totals =	$945.72		$1,040.6263	$1,040.61	$1,040.60	$1,040.70