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	$83.49	12.844%	$94.2135	$94.21	$94.20	$94.20
Purchase #2	$48.57	11.628%	$54.2177	$54.22	$54.20	$54.20
Purchase #3	$166.60	6.546%	$177.5056	$177.51	$177.50	$177.50
Purchase #4	$247.93	11.455%	$276.3304	$276.33	$276.35	$276.30
Purchase #5	$53.30	11.257%	$59.3	$59.30	$59.30	$59.30
Purchase #6	$196.53	13.411%	$222.8866	$222.89	$222.90	$222.90
Purchase #7	$125.43	13.677%	$142.5851	$142.59	$142.60	$142.60
7 purchase totals =	$921.85		$1,027.0389	$1,027.05	$1,027.05	$1,027.00