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	$92.92	13.494%	$105.4586	$105.46	$105.45	$105.50
Purchase #2	$243.85	12.767%	$274.9823	$274.98	$275.00	$275.00
Purchase #3	$7.39	12.447%	$8.3098	$8.31	$8.30	$8.30
Purchase #4	$215.96	10.557%	$238.7589	$238.76	$238.75	$238.80
Purchase #5	$40.37	10.319%	$44.5358	$44.54	$44.55	$44.50
Purchase #6	$145.27	4.282%	$151.4905	$151.49	$151.50	$151.50
Purchase #7	$194.51	6.148%	$206.4685	$206.47	$206.45	$206.50
7 purchase totals =	$940.27		$1,030.0044	$1,030.01	$1,030.00	$1,030.10