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	$87.43	10.328%	$96.4598	$96.46	$96.45	$96.50
Purchase #2	$71.84	10.446%	$79.3444	$79.34	$79.35	$79.30
Purchase #3	$62.56	3.760%	$64.9123	$64.91	$64.90	$64.90
Purchase #4	$48.89	8.124%	$52.8618	$52.86	$52.85	$52.90
Purchase #5	$217.88	12.720%	$245.5943	$245.59	$245.60	$245.60
Purchase #6	$39.67	3.598%	$41.0973	$41.10	$41.10	$41.10
Purchase #7	$16.79	8.796%	$18.2668	$18.27	$18.25	$18.30
7 purchase totals =	$545.06		$598.5367	$598.53	$598.50	$598.60