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	$148.69	12.713%	$167.593	$167.59	$167.60	$167.60
Purchase #2	$241.84	13.323%	$274.0603	$274.06	$274.05	$274.10
Purchase #3	$214.47	11.184%	$238.4563	$238.46	$238.45	$238.50
Purchase #4	$138.73	5.630%	$146.5405	$146.54	$146.55	$146.50
Purchase #5	$53.61	5.535%	$56.5773	$56.58	$56.60	$56.60
Purchase #6	$32.62	11.777%	$36.4617	$36.46	$36.45	$36.50
Purchase #7	$120.80	7.199%	$129.4964	$129.50	$129.50	$129.50
7 purchase totals =	$950.76		$1,049.1855	$1,049.19	$1,049.20	$1,049.30