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	$61.91	5.545%	$65.3429	$65.34	$65.35	$65.30
Purchase #2	$8.82	5.462%	$9.3017	$9.30	$9.30	$9.30
Purchase #3	$79.89	11.736%	$89.2659	$89.27	$89.25	$89.30
Purchase #4	$195.62	11.481%	$218.0791	$218.08	$218.10	$218.10
Purchase #5	$38.56	8.472%	$41.8268	$41.83	$41.85	$41.80
Purchase #6	$118.34	5.173%	$124.4617	$124.46	$124.45	$124.50
Purchase #7	$48.87	8.598%	$53.0718	$53.07	$53.05	$53.10
7 purchase totals =	$552.01		$601.3499	$601.35	$601.35	$601.40