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	$169.33	8.582%	$183.8619	$183.86	$183.85	$183.90
Purchase #2	$197.49	8.217%	$213.7178	$213.72	$213.70	$213.70
Purchase #3	$240.81	4.431%	$251.4803	$251.48	$251.50	$251.50
Purchase #4	$77.67	3.445%	$80.3457	$80.35	$80.35	$80.30
Purchase #5	$50.73	13.524%	$57.5907	$57.59	$57.60	$57.60
Purchase #6	$188.89	13.776%	$214.9115	$214.91	$214.90	$214.90
Purchase #7	$151.31	9.229%	$165.2744	$165.27	$165.25	$165.30
7 purchase totals =	$1,076.23		$1,167.1823	$1,167.18	$1,167.15	$1,167.20