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	$100.84	9.575%	$110.4954	$110.50	$110.50	$110.50
Purchase #2	$22.85	13.511%	$25.9373	$25.94	$25.95	$25.90
Purchase #3	$183.39	9.428%	$200.68	$200.68	$200.70	$200.70
Purchase #4	$47.40	7.369%	$50.8929	$50.89	$50.90	$50.90
Purchase #5	$96.59	9.263%	$105.5371	$105.54	$105.55	$105.50
Purchase #6	$170.62	4.509%	$178.3133	$178.31	$178.30	$178.30
Purchase #7	$37.35	11.595%	$41.6807	$41.68	$41.70	$41.70
7 purchase totals =	$659.04		$713.5367	$713.54	$713.60	$713.50