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	$78.97	3.305%	$81.58	$81.58	$81.60	$81.60
Purchase #2	$243.76	5.266%	$256.5964	$256.60	$256.60	$256.60
Purchase #3	$78.58	12.228%	$88.1888	$88.19	$88.20	$88.20
Purchase #4	$12.58	7.355%	$13.5053	$13.51	$13.50	$13.50
Purchase #5	$82.90	3.362%	$85.6871	$85.69	$85.70	$85.70
Purchase #6	$161.48	8.407%	$175.0556	$175.06	$175.05	$175.10
Purchase #7	$40.34	12.109%	$45.2248	$45.22	$45.20	$45.20
7 purchase totals =	$698.61		$745.8380	$745.85	$745.85	$745.90