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	$211.89	8.326%	$229.532	$229.53	$229.55	$229.50
Purchase #2	$231.87	6.319%	$246.5219	$246.52	$246.50	$246.50
Purchase #3	$112.87	9.115%	$123.1581	$123.16	$123.15	$123.20
Purchase #4	$245.83	6.773%	$262.4801	$262.48	$262.50	$262.50
Purchase #5	$223.54	12.618%	$251.7463	$251.75	$251.75	$251.70
Purchase #6	$80.48	12.727%	$90.7227	$90.72	$90.70	$90.70
Purchase #7	$157.88	9.347%	$172.637	$172.64	$172.65	$172.60
7 purchase totals =	$1,264.36		$1,376.7981	$1,376.80	$1,376.80	$1,376.70