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	$74.94	11.567%	$83.6083	$83.61	$83.60	$83.60
Purchase #2	$239.29	6.708%	$255.3416	$255.34	$255.35	$255.30
Purchase #3	$58.90	5.676%	$62.2432	$62.24	$62.25	$62.20
Purchase #4	$192.59	8.659%	$209.2664	$209.27	$209.25	$209.30
Purchase #5	$229.31	12.788%	$258.6342	$258.63	$258.65	$258.60
Purchase #6	$200.74	4.313%	$209.3979	$209.40	$209.40	$209.40
Purchase #7	$20.87	9.819%	$22.9192	$22.92	$22.90	$22.90
7 purchase totals =	$1,016.64		$1,101.4108	$1,101.41	$1,101.40	$1,101.30