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	$42.28	10.872%	$46.8767	$46.88	$46.90	$46.90
Purchase #2	$243.77	10.686%	$269.8193	$269.82	$269.80	$269.80
Purchase #3	$38.95	13.244%	$44.1085	$44.11	$44.10	$44.10
Purchase #4	$225.45	6.574%	$240.2711	$240.27	$240.25	$240.30
Purchase #5	$99.25	7.728%	$106.92	$106.92	$106.90	$106.90
Purchase #6	$163.92	5.819%	$173.4585	$173.46	$173.45	$173.50
Purchase #7	$125.29	7.644%	$134.8672	$134.87	$134.85	$134.90
7 purchase totals =	$938.91		$1,016.3213	$1,016.33	$1,016.25	$1,016.40