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	$41.77	8.356%	$45.2603	$45.26	$45.25	$45.30
Purchase #2	$112.69	6.771%	$120.3202	$120.32	$120.30	$120.30
Purchase #3	$208.30	11.376%	$231.9962	$232.00	$232.00	$232.00
Purchase #4	$190.31	4.490%	$198.8549	$198.85	$198.85	$198.90
Purchase #5	$190.90	4.825%	$200.1109	$200.11	$200.10	$200.10
Purchase #6	$90.88	9.168%	$99.2119	$99.21	$99.20	$99.20
Purchase #7	$138.90	8.728%	$151.0232	$151.02	$151.00	$151.00
7 purchase totals =	$973.75		$1,046.7776	$1,046.77	$1,046.70	$1,046.80