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	$210.89	10.803%	$233.6724	$233.67	$233.65	$233.70
Purchase #2	$73.94	10.143%	$81.4397	$81.44	$81.45	$81.40
Purchase #3	$126.34	3.218%	$130.4056	$130.41	$130.40	$130.40
Purchase #4	$137.79	9.535%	$150.9283	$150.93	$150.95	$150.90
Purchase #5	$245.95	4.180%	$256.2307	$256.23	$256.25	$256.20
Purchase #6	$55.51	12.436%	$62.4132	$62.41	$62.40	$62.40
Purchase #7	$212.73	11.322%	$236.8153	$236.82	$236.80	$236.80
7 purchase totals =	$1,063.15		$1,151.9052	$1,151.91	$1,151.90	$1,151.80