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	$180.81	6.801%	$193.1069	$193.11	$193.10	$193.10
Purchase #2	$47.52	10.107%	$52.3228	$52.32	$52.30	$52.30
Purchase #3	$170.55	10.760%	$188.9012	$188.90	$188.90	$188.90
Purchase #4	$11.64	13.679%	$13.2322	$13.23	$13.25	$13.20
Purchase #5	$113.70	11.454%	$126.7232	$126.72	$126.70	$126.70
Purchase #6	$242.31	10.446%	$267.6217	$267.62	$267.60	$267.60
Purchase #7	$209.30	6.827%	$223.5889	$223.59	$223.60	$223.60
7 purchase totals =	$975.83		$1,065.4969	$1,065.49	$1,065.45	$1,065.40