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	$106.64	4.452%	$111.3876	$111.39	$111.40	$111.40
Purchase #2	$119.49	9.368%	$130.6838	$130.68	$130.70	$130.70
Purchase #3	$232.59	13.457%	$263.8896	$263.89	$263.90	$263.90
Purchase #4	$53.77	10.346%	$59.333	$59.33	$59.35	$59.30
Purchase #5	$62.90	6.472%	$66.9709	$66.97	$66.95	$67.00
Purchase #6	$219.53	13.587%	$249.3575	$249.36	$249.35	$249.40
Purchase #7	$40.27	7.754%	$43.3925	$43.39	$43.40	$43.40
7 purchase totals =	$835.19		$925.0149	$925.01	$925.05	$925.10