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	$44.94	11.442%	$50.082	$50.08	$50.10	$50.10
Purchase #2	$28.54	12.638%	$32.1469	$32.15	$32.15	$32.10
Purchase #3	$165.79	4.513%	$173.2721	$173.27	$173.25	$173.30
Purchase #4	$98.74	3.353%	$102.0508	$102.05	$102.05	$102.10
Purchase #5	$63.72	6.107%	$67.6114	$67.61	$67.60	$67.60
Purchase #6	$220.71	11.307%	$245.6657	$245.67	$245.65	$245.70
Purchase #7	$37.86	12.242%	$42.4948	$42.49	$42.50	$42.50
7 purchase totals =	$660.30		$713.3237	$713.32	$713.30	$713.40