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	$220.53	12.496%	$248.0874	$248.09	$248.10	$248.10
Purchase #2	$59.35	4.647%	$62.108	$62.11	$62.10	$62.10
Purchase #3	$159.52	12.457%	$179.3914	$179.39	$179.40	$179.40
Purchase #4	$103.39	8.287%	$111.9579	$111.96	$111.95	$112.00
Purchase #5	$141.59	10.336%	$156.2247	$156.22	$156.20	$156.20
Purchase #6	$11.48	5.689%	$12.1331	$12.13	$12.15	$12.10
Purchase #7	$230.32	8.185%	$249.1717	$249.17	$249.15	$249.20
7 purchase totals =	$926.18		$1,019.0742	$1,019.07	$1,019.05	$1,019.10