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	$45.49	7.314%	$48.8171	$48.82	$48.80	$48.80
Purchase #2	$59.69	4.140%	$62.1612	$62.16	$62.15	$62.20
Purchase #3	$112.43	3.869%	$116.7799	$116.78	$116.80	$116.80
Purchase #4	$129.66	11.809%	$144.9715	$144.97	$144.95	$145.00
Purchase #5	$84.30	7.830%	$90.9007	$90.90	$90.90	$90.90
Purchase #6	$148.99	12.470%	$167.5691	$167.57	$167.55	$167.60
Purchase #7	$145.55	7.353%	$156.2523	$156.25	$156.25	$156.30
7 purchase totals =	$726.11		$787.4518	$787.45	$787.40	$787.60