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	$138.66	9.325%	$151.59	$151.59	$151.60	$151.60
Purchase #2	$95.85	5.326%	$100.955	$100.96	$100.95	$101.00
Purchase #3	$90.36	3.234%	$93.2822	$93.28	$93.30	$93.30
Purchase #4	$149.38	11.352%	$166.3376	$166.34	$166.35	$166.30
Purchase #5	$46.63	11.782%	$52.1239	$52.12	$52.10	$52.10
Purchase #6	$89.80	12.176%	$100.734	$100.73	$100.75	$100.70
Purchase #7	$225.90	9.721%	$247.8597	$247.86	$247.85	$247.90
7 purchase totals =	$836.58		$912.8824	$912.88	$912.90	$912.90