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	$112.64	12.328%	$126.5263	$126.53	$126.55	$126.50
Purchase #2	$73.30	5.347%	$77.2194	$77.22	$77.20	$77.20
Purchase #3	$81.85	9.482%	$89.611	$89.61	$89.60	$89.60
Purchase #4	$131.49	12.152%	$147.4687	$147.47	$147.45	$147.50
Purchase #5	$221.38	8.729%	$240.7043	$240.70	$240.70	$240.70
Purchase #6	$208.68	8.489%	$226.3948	$226.39	$226.40	$226.40
Purchase #7	$215.89	8.196%	$233.5843	$233.58	$233.60	$233.60
7 purchase totals =	$1,045.23		$1,141.5088	$1,141.50	$1,141.50	$1,141.50