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	$187.41	4.865%	$196.5275	$196.53	$196.55	$196.50
Purchase #2	$123.97	3.642%	$128.485	$128.49	$128.50	$128.50
Purchase #3	$71.49	8.265%	$77.3986	$77.40	$77.40	$77.40
Purchase #4	$133.85	4.227%	$139.5078	$139.51	$139.50	$139.50
Purchase #5	$110.54	8.725%	$120.1846	$120.18	$120.20	$120.20
Purchase #6	$131.86	10.747%	$146.031	$146.03	$146.05	$146.00
Purchase #7	$237.69	4.514%	$248.4193	$248.42	$248.40	$248.40
7 purchase totals =	$996.81		$1,056.5538	$1,056.56	$1,056.60	$1,056.50