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	$106.32	4.270%	$110.8599	$110.86	$110.85	$110.90
Purchase #2	$62.44	12.240%	$70.0827	$70.08	$70.10	$70.10
Purchase #3	$84.36	5.697%	$89.166	$89.17	$89.15	$89.20
Purchase #4	$209.30	5.276%	$220.3427	$220.34	$220.35	$220.30
Purchase #5	$17.25	10.637%	$19.0849	$19.08	$19.10	$19.10
Purchase #6	$94.61	11.594%	$105.5791	$105.58	$105.60	$105.60
Purchase #7	$106.47	4.809%	$111.5901	$111.59	$111.60	$111.60
7 purchase totals =	$680.75		$726.7054	$726.70	$726.75	$726.80