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	$206.31	8.510%	$223.867	$223.87	$223.85	$223.90
Purchase #2	$61.79	6.181%	$65.6092	$65.61	$65.60	$65.60
Purchase #3	$83.89	6.465%	$89.3135	$89.31	$89.30	$89.30
Purchase #4	$231.66	4.519%	$242.1287	$242.13	$242.15	$242.10
Purchase #5	$112.86	13.862%	$128.5047	$128.50	$128.50	$128.50
Purchase #6	$59.33	12.654%	$66.8376	$66.84	$66.85	$66.80
Purchase #7	$151.75	12.795%	$171.1664	$171.17	$171.15	$171.20
7 purchase totals =	$907.59		$987.4271	$987.43	$987.40	$987.40