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	$241.71	12.227%	$271.2639	$271.26	$271.25	$271.30
Purchase #2	$161.64	4.484%	$168.8879	$168.89	$168.90	$168.90
Purchase #3	$175.65	5.609%	$185.5022	$185.50	$185.50	$185.50
Purchase #4	$139.58	13.576%	$158.5294	$158.53	$158.55	$158.50
Purchase #5	$12.73	6.772%	$13.5921	$13.59	$13.60	$13.60
Purchase #6	$120.56	5.596%	$127.3065	$127.31	$127.30	$127.30
Purchase #7	$171.37	9.871%	$188.2859	$188.29	$188.30	$188.30
7 purchase totals =	$1,023.24		$1,113.3679	$1,113.37	$1,113.40	$1,113.40