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	$203.56	7.675%	$219.1832	$219.18	$219.20	$219.20
Purchase #2	$37.79	12.799%	$42.6267	$42.63	$42.65	$42.60
Purchase #3	$122.39	6.613%	$130.4837	$130.48	$130.50	$130.50
Purchase #4	$80.93	11.871%	$90.5372	$90.54	$90.55	$90.50
Purchase #5	$229.85	3.102%	$236.9799	$236.98	$237.00	$237.00
Purchase #6	$248.56	11.383%	$276.8536	$276.85	$276.85	$276.90
Purchase #7	$233.89	8.566%	$253.925	$253.93	$253.95	$253.90
7 purchase totals =	$1,156.97		$1,250.5893	$1,250.59	$1,250.70	$1,250.60