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	$190.39	11.388%	$212.0716	$212.07	$212.05	$212.10
Purchase #2	$93.54	12.410%	$105.1483	$105.15	$105.15	$105.10
Purchase #3	$100.74	11.745%	$112.5719	$112.57	$112.55	$112.60
Purchase #4	$162.30	6.830%	$173.3851	$173.39	$173.40	$173.40
Purchase #5	$228.53	13.166%	$258.6183	$258.62	$258.60	$258.60
Purchase #6	$247.78	7.665%	$266.7723	$266.77	$266.75	$266.80
Purchase #7	$32.70	5.221%	$34.4073	$34.41	$34.40	$34.40
7 purchase totals =	$1,055.98		$1,162.9748	$1,162.98	$1,162.90	$1,163.00