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	$169.62	7.716%	$182.7079	$182.71	$182.70	$182.70
Purchase #2	$152.60	8.653%	$165.8045	$165.80	$165.80	$165.80
Purchase #3	$140.81	4.291%	$146.8522	$146.85	$146.85	$146.90
Purchase #4	$113.95	11.513%	$127.0691	$127.07	$127.05	$127.10
Purchase #5	$103.90	8.765%	$113.0068	$113.01	$113.00	$113.00
Purchase #6	$247.39	8.241%	$267.7774	$267.78	$267.80	$267.80
Purchase #7	$99.46	5.847%	$105.2754	$105.28	$105.30	$105.30
7 purchase totals =	$1,027.73		$1,108.4933	$1,108.50	$1,108.50	$1,108.60