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	$174.42	9.741%	$191.4103	$191.41	$191.40	$191.40
Purchase #2	$181.89	11.861%	$203.464	$203.46	$203.45	$203.50
Purchase #3	$148.58	12.345%	$166.9222	$166.92	$166.90	$166.90
Purchase #4	$113.57	8.754%	$123.5119	$123.51	$123.50	$123.50
Purchase #5	$235.88	9.332%	$257.8923	$257.89	$257.90	$257.90
Purchase #6	$138.42	10.219%	$152.5651	$152.57	$152.55	$152.60
Purchase #7	$222.91	8.489%	$241.8328	$241.83	$241.85	$241.80
7 purchase totals =	$1,215.67		$1,337.5986	$1,337.59	$1,337.55	$1,337.60