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	$149.40	4.332%	$155.872	$155.87	$155.85	$155.90
Purchase #2	$166.44	9.603%	$182.4232	$182.42	$182.40	$182.40
Purchase #3	$37.60	12.119%	$42.1567	$42.16	$42.15	$42.20
Purchase #4	$95.33	13.627%	$108.3206	$108.32	$108.30	$108.30
Purchase #5	$175.55	5.526%	$185.2509	$185.25	$185.25	$185.30
Purchase #6	$7.87	12.830%	$8.8797	$8.88	$8.90	$8.90
Purchase #7	$18.60	12.828%	$20.986	$20.99	$21.00	$21.00
7 purchase totals =	$650.79		$703.8891	$703.89	$703.85	$704.00