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	$95.72	5.119%	$100.6199	$100.62	$100.60	$100.60
Purchase #2	$226.85	8.671%	$246.5202	$246.52	$246.50	$246.50
Purchase #3	$94.64	5.333%	$99.6872	$99.69	$99.70	$99.70
Purchase #4	$175.39	6.700%	$187.1411	$187.14	$187.15	$187.10
Purchase #5	$175.85	11.629%	$196.2996	$196.30	$196.30	$196.30
Purchase #6	$177.76	10.644%	$196.6808	$196.68	$196.70	$196.70
Purchase #7	$59.86	7.686%	$64.4608	$64.46	$64.45	$64.50
7 purchase totals =	$1,006.07		$1,091.4096	$1,091.41	$1,091.40	$1,091.40