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	$71.51	6.274%	$75.9965	$76.00	$76.00	$76.00
Purchase #2	$151.43	13.413%	$171.7413	$171.74	$171.75	$171.70
Purchase #3	$19.49	6.655%	$20.7871	$20.79	$20.80	$20.80
Purchase #4	$219.26	10.209%	$241.6443	$241.64	$241.65	$241.60
Purchase #5	$222.74	10.145%	$245.337	$245.34	$245.35	$245.30
Purchase #6	$86.32	3.284%	$89.1547	$89.15	$89.15	$89.20
Purchase #7	$80.87	11.287%	$89.9978	$90.00	$90.00	$90.00
7 purchase totals =	$851.62		$934.6587	$934.66	$934.70	$934.60