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	$204.44	9.419%	$223.6962	$223.70	$223.70	$223.70
Purchase #2	$36.56	4.784%	$38.309	$38.31	$38.30	$38.30
Purchase #3	$209.72	3.699%	$217.4775	$217.48	$217.50	$217.50
Purchase #4	$105.68	5.328%	$111.3106	$111.31	$111.30	$111.30
Purchase #5	$16.31	13.177%	$18.4592	$18.46	$18.45	$18.50
Purchase #6	$223.42	4.196%	$232.7947	$232.79	$232.80	$232.80
Purchase #7	$212.66	8.781%	$231.3337	$231.33	$231.35	$231.30
7 purchase totals =	$1,008.79		$1,073.3809	$1,073.38	$1,073.40	$1,073.40