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	$207.90	7.507%	$223.5071	$223.51	$223.50	$223.50
Purchase #2	$41.91	9.116%	$45.7305	$45.73	$45.75	$45.70
Purchase #3	$72.38	5.383%	$76.2762	$76.28	$76.30	$76.30
Purchase #4	$165.26	8.425%	$179.1832	$179.18	$179.20	$179.20
Purchase #5	$235.33	7.349%	$252.6244	$252.62	$252.60	$252.60
Purchase #6	$6.98	10.196%	$7.6917	$7.69	$7.70	$7.70
Purchase #7	$195.34	11.834%	$218.4565	$218.46	$218.45	$218.50
7 purchase totals =	$925.10		$1,003.4696	$1,003.47	$1,003.50	$1,003.50