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	$211.41	11.809%	$236.3754	$236.38	$236.40	$236.40
Purchase #2	$208.81	6.686%	$222.771	$222.77	$222.75	$222.80
Purchase #3	$219.48	4.714%	$229.8263	$229.83	$229.85	$229.80
Purchase #4	$37.28	10.662%	$41.2548	$41.25	$41.25	$41.30
Purchase #5	$236.68	12.139%	$265.4106	$265.41	$265.40	$265.40
Purchase #6	$42.27	10.535%	$46.7231	$46.72	$46.70	$46.70
Purchase #7	$59.32	8.341%	$64.2679	$64.27	$64.25	$64.30
7 purchase totals =	$1,015.25		$1,106.6291	$1,106.63	$1,106.60	$1,106.70