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	$177.27	7.388%	$190.3667	$190.37	$190.35	$190.40
Purchase #2	$85.61	12.319%	$96.1563	$96.16	$96.15	$96.20
Purchase #3	$243.44	11.617%	$271.7204	$271.72	$271.70	$271.70
Purchase #4	$246.92	12.766%	$278.4418	$278.44	$278.45	$278.40
Purchase #5	$69.92	12.832%	$78.8921	$78.89	$78.90	$78.90
Purchase #6	$78.41	5.760%	$82.9264	$82.93	$82.95	$82.90
Purchase #7	$105.79	7.836%	$114.0797	$114.08	$114.10	$114.10
7 purchase totals =	$1,007.36		$1,112.5834	$1,112.59	$1,112.60	$1,112.60