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	$48.40	7.700%	$52.1268	$52.13	$52.15	$52.10
Purchase #2	$98.55	6.833%	$105.2839	$105.28	$105.30	$105.30
Purchase #3	$159.45	6.490%	$169.7983	$169.80	$169.80	$169.80
Purchase #4	$210.87	6.412%	$224.391	$224.39	$224.40	$224.40
Purchase #5	$50.50	9.248%	$55.1702	$55.17	$55.15	$55.20
Purchase #6	$209.84	6.663%	$223.8216	$223.82	$223.80	$223.80
Purchase #7	$48.25	9.265%	$52.7204	$52.72	$52.70	$52.70
7 purchase totals =	$825.86		$883.3122	$883.31	$883.30	$883.30