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	$84.90	12.754%	$95.7281	$95.73	$95.75	$95.70
Purchase #2	$99.31	12.194%	$111.4199	$111.42	$111.40	$111.40
Purchase #3	$223.89	7.139%	$239.8735	$239.87	$239.85	$239.90
Purchase #4	$11.93	6.782%	$12.7391	$12.74	$12.75	$12.70
Purchase #5	$130.33	10.579%	$144.1176	$144.12	$144.10	$144.10
Purchase #6	$238.64	11.541%	$266.1814	$266.18	$266.20	$266.20
Purchase #7	$248.59	6.357%	$264.3929	$264.39	$264.40	$264.40
7 purchase totals =	$1,037.59		$1,134.4525	$1,134.45	$1,134.45	$1,134.40