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	$169.35	9.259%	$185.0301	$185.03	$185.05	$185.00
Purchase #2	$108.64	13.431%	$123.2314	$123.23	$123.25	$123.20
Purchase #3	$44.72	4.173%	$46.5862	$46.59	$46.60	$46.60
Purchase #4	$175.84	7.760%	$189.4852	$189.49	$189.50	$189.50
Purchase #5	$58.50	10.782%	$64.8075	$64.81	$64.80	$64.80
Purchase #6	$106.32	10.396%	$117.373	$117.37	$117.35	$117.40
Purchase #7	$169.79	4.184%	$176.894	$176.89	$176.90	$176.90
7 purchase totals =	$833.16		$903.4074	$903.41	$903.45	$903.40