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	$244.94	9.709%	$268.7212	$268.72	$268.70	$268.70
Purchase #2	$148.89	11.129%	$165.46	$165.46	$165.45	$165.50
Purchase #3	$61.84	9.202%	$67.5305	$67.53	$67.55	$67.50
Purchase #4	$250.79	11.350%	$279.2547	$279.25	$279.25	$279.30
Purchase #5	$29.47	11.766%	$32.9374	$32.94	$32.95	$32.90
Purchase #6	$159.60	6.116%	$169.3611	$169.36	$169.35	$169.40
Purchase #7	$216.94	12.705%	$244.5022	$244.50	$244.50	$244.50
7 purchase totals =	$1,112.47		$1,227.7671	$1,227.76	$1,227.75	$1,227.80