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	$90.31	5.546%	$95.3186	$95.32	$95.30	$95.30
Purchase #2	$205.80	3.116%	$212.2127	$212.21	$212.20	$212.20
Purchase #3	$64.65	5.182%	$68.0002	$68.00	$68.00	$68.00
Purchase #4	$243.67	7.673%	$262.3668	$262.37	$262.35	$262.40
Purchase #5	$31.80	4.162%	$33.1235	$33.12	$33.10	$33.10
Purchase #6	$106.74	4.816%	$111.8806	$111.88	$111.90	$111.90
Purchase #7	$209.33	13.222%	$237.0076	$237.01	$237.00	$237.00
7 purchase totals =	$952.30		$1,019.9100	$1,019.91	$1,019.85	$1,019.90