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	$169.46	12.403%	$190.4781	$190.48	$190.50	$190.50
Purchase #2	$41.84	6.538%	$44.5755	$44.58	$44.60	$44.60
Purchase #3	$68.48	3.823%	$71.098	$71.10	$71.10	$71.10
Purchase #4	$138.80	5.609%	$146.5853	$146.59	$146.60	$146.60
Purchase #5	$96.77	9.479%	$105.9428	$105.94	$105.95	$105.90
Purchase #6	$183.30	6.259%	$194.7727	$194.77	$194.75	$194.80
Purchase #7	$220.41	13.737%	$250.6877	$250.69	$250.70	$250.70
7 purchase totals =	$919.06		$1,004.1401	$1,004.15	$1,004.20	$1,004.20