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	$151.41	13.505%	$171.8579	$171.86	$171.85	$171.90
Purchase #2	$100.84	13.630%	$114.5845	$114.58	$114.60	$114.60
Purchase #3	$17.82	4.755%	$18.6673	$18.67	$18.65	$18.70
Purchase #4	$214.58	9.790%	$235.5874	$235.59	$235.60	$235.60
Purchase #5	$132.71	5.470%	$139.9692	$139.97	$139.95	$140.00
Purchase #6	$151.26	11.615%	$168.8288	$168.83	$168.85	$168.80
Purchase #7	$84.84	9.618%	$92.9999	$93.00	$93.00	$93.00
7 purchase totals =	$853.46		$942.4950	$942.50	$942.50	$942.60