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	$140.71	11.254%	$156.5455	$156.55	$156.55	$156.50
Purchase #2	$74.85	10.502%	$82.7107	$82.71	$82.70	$82.70
Purchase #3	$95.79	5.281%	$100.8487	$100.85	$100.85	$100.80
Purchase #4	$204.38	7.595%	$219.9027	$219.90	$219.90	$219.90
Purchase #5	$236.91	11.773%	$264.8014	$264.80	$264.80	$264.80
Purchase #6	$182.83	4.163%	$190.4412	$190.44	$190.45	$190.40
Purchase #7	$210.93	11.149%	$234.4466	$234.45	$234.45	$234.40
7 purchase totals =	$1,146.40		$1,249.6968	$1,249.70	$1,249.70	$1,249.50