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	$48.84	9.273%	$53.3689	$53.37	$53.35	$53.40
Purchase #2	$58.34	7.390%	$62.6513	$62.65	$62.65	$62.70
Purchase #3	$161.74	4.843%	$169.5731	$169.57	$169.55	$169.60
Purchase #4	$153.25	12.161%	$171.8867	$171.89	$171.90	$171.90
Purchase #5	$125.54	4.489%	$131.1755	$131.18	$131.20	$131.20
Purchase #6	$182.53	7.565%	$196.3384	$196.34	$196.35	$196.30
Purchase #7	$158.91	13.406%	$180.2135	$180.21	$180.20	$180.20
7 purchase totals =	$889.15		$965.2074	$965.21	$965.20	$965.30