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	$81.33	10.285%	$89.6948	$89.69	$89.70	$89.70
Purchase #2	$180.72	5.614%	$190.8656	$190.87	$190.85	$190.90
Purchase #3	$243.81	9.675%	$267.3986	$267.40	$267.40	$267.40
Purchase #4	$231.25	8.776%	$251.5445	$251.54	$251.55	$251.50
Purchase #5	$64.67	4.850%	$67.8065	$67.81	$67.80	$67.80
Purchase #6	$144.75	4.437%	$151.1726	$151.17	$151.15	$151.20
Purchase #7	$77.66	13.779%	$88.3608	$88.36	$88.35	$88.40
7 purchase totals =	$1,024.19		$1,106.8434	$1,106.84	$1,106.80	$1,106.90