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	$196.86	13.207%	$222.8593	$222.86	$222.85	$222.90
Purchase #2	$178.39	4.632%	$186.653	$186.65	$186.65	$186.70
Purchase #3	$224.53	10.717%	$248.5929	$248.59	$248.60	$248.60
Purchase #4	$19.65	11.607%	$21.9308	$21.93	$21.95	$21.90
Purchase #5	$247.37	12.134%	$277.3859	$277.39	$277.40	$277.40
Purchase #6	$165.29	8.623%	$179.543	$179.54	$179.55	$179.50
Purchase #7	$142.79	6.258%	$151.7258	$151.73	$151.75	$151.70
7 purchase totals =	$1,174.88		$1,288.6907	$1,288.69	$1,288.75	$1,288.70