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	$97.31	6.758%	$103.8862	$103.89	$103.90	$103.90
Purchase #2	$73.46	6.735%	$78.4075	$78.41	$78.40	$78.40
Purchase #3	$90.80	9.465%	$99.3942	$99.39	$99.40	$99.40
Purchase #4	$93.96	6.485%	$100.0533	$100.05	$100.05	$100.10
Purchase #5	$50.25	6.864%	$53.6992	$53.70	$53.70	$53.70
Purchase #6	$194.79	8.286%	$210.9303	$210.93	$210.95	$210.90
Purchase #7	$223.47	11.664%	$249.5355	$249.54	$249.55	$249.50
7 purchase totals =	$824.04		$895.9062	$895.91	$895.95	$895.90