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	$156.89	10.190%	$172.8771	$172.88	$172.90	$172.90
Purchase #2	$17.56	10.415%	$19.3889	$19.39	$19.40	$19.40
Purchase #3	$33.31	13.802%	$37.9074	$37.91	$37.90	$37.90
Purchase #4	$223.58	4.557%	$233.7685	$233.77	$233.75	$233.80
Purchase #5	$229.49	7.431%	$246.5434	$246.54	$246.55	$246.50
Purchase #6	$211.71	4.727%	$221.7175	$221.72	$221.70	$221.70
Purchase #7	$148.31	4.716%	$155.3043	$155.30	$155.30	$155.30
7 purchase totals =	$1,020.85		$1,087.5071	$1,087.51	$1,087.50	$1,087.50