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	$91.36	9.605%	$100.1351	$100.14	$100.15	$100.10
Purchase #2	$195.47	4.586%	$204.4343	$204.43	$204.45	$204.40
Purchase #3	$142.56	9.228%	$155.7154	$155.72	$155.70	$155.70
Purchase #4	$243.81	13.253%	$276.1221	$276.12	$276.10	$276.10
Purchase #5	$140.66	3.822%	$146.036	$146.04	$146.05	$146.00
Purchase #6	$135.83	3.821%	$141.0201	$141.02	$141.00	$141.00
Purchase #7	$37.28	8.782%	$40.5539	$40.55	$40.55	$40.60
7 purchase totals =	$986.97		$1,064.0169	$1,064.02	$1,064.00	$1,063.90