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	$234.36	4.673%	$245.3116	$245.31	$245.30	$245.30
Purchase #2	$92.62	11.287%	$103.074	$103.07	$103.05	$103.10
Purchase #3	$163.76	10.480%	$180.922	$180.92	$180.90	$180.90
Purchase #4	$216.36	11.310%	$240.8303	$240.83	$240.85	$240.80
Purchase #5	$55.72	6.814%	$59.5168	$59.52	$59.50	$59.50
Purchase #6	$217.37	11.536%	$242.4458	$242.45	$242.45	$242.40
Purchase #7	$90.40	7.256%	$96.9594	$96.96	$96.95	$97.00
7 purchase totals =	$1,070.59		$1,169.0599	$1,169.06	$1,169.00	$1,169.00