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	$47.69	10.694%	$52.79	$52.79	$52.80	$52.80
Purchase #2	$105.86	8.448%	$114.8031	$114.80	$114.80	$114.80
Purchase #3	$93.65	7.283%	$100.4705	$100.47	$100.45	$100.50
Purchase #4	$238.75	6.322%	$253.8438	$253.84	$253.85	$253.80
Purchase #5	$64.44	11.554%	$71.8854	$71.89	$71.90	$71.90
Purchase #6	$46.54	11.738%	$52.0029	$52.00	$52.00	$52.00
Purchase #7	$108.37	6.267%	$115.1615	$115.16	$115.15	$115.20
7 purchase totals =	$705.30		$760.9572	$760.95	$760.95	$761.00