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	$152.28	11.396%	$169.6338	$169.63	$169.65	$169.60
Purchase #2	$128.51	3.198%	$132.6197	$132.62	$132.60	$132.60
Purchase #3	$248.68	8.552%	$269.9471	$269.95	$269.95	$269.90
Purchase #4	$181.72	7.864%	$196.0105	$196.01	$196.00	$196.00
Purchase #5	$87.99	4.603%	$92.0402	$92.04	$92.05	$92.00
Purchase #6	$17.52	5.761%	$18.5293	$18.53	$18.55	$18.50
Purchase #7	$163.53	11.364%	$182.1135	$182.11	$182.10	$182.10
7 purchase totals =	$980.23		$1,060.8941	$1,060.89	$1,060.90	$1,060.70