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	$164.98	10.230%	$181.8575	$181.86	$181.85	$181.90
Purchase #2	$26.51	11.145%	$29.4645	$29.46	$29.45	$29.50
Purchase #3	$89.56	11.541%	$99.8961	$99.90	$99.90	$99.90
Purchase #4	$150.72	3.317%	$155.7194	$155.72	$155.70	$155.70
Purchase #5	$227.96	9.468%	$249.5433	$249.54	$249.55	$249.50
Purchase #6	$166.89	9.413%	$182.5994	$182.60	$182.60	$182.60
Purchase #7	$44.45	12.496%	$50.0045	$50.00	$50.00	$50.00
7 purchase totals =	$871.07		$949.0847	$949.08	$949.05	$949.10