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	$165.69	7.545%	$178.1913	$178.19	$178.20	$178.20
Purchase #2	$240.46	12.830%	$271.311	$271.31	$271.30	$271.30
Purchase #3	$158.47	8.731%	$172.306	$172.31	$172.30	$172.30
Purchase #4	$157.66	8.319%	$170.7757	$170.78	$170.80	$170.80
Purchase #5	$54.65	11.657%	$61.0206	$61.02	$61.00	$61.00
Purchase #6	$46.80	13.459%	$53.0988	$53.10	$53.10	$53.10
Purchase #7	$233.83	3.573%	$242.1847	$242.18	$242.20	$242.20
7 purchase totals =	$1,057.56		$1,148.8881	$1,148.89	$1,148.90	$1,148.90