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	$175.56	6.208%	$186.4588	$186.46	$186.45	$186.50
Purchase #2	$91.53	4.720%	$95.8502	$95.85	$95.85	$95.90
Purchase #3	$150.37	3.679%	$155.9021	$155.90	$155.90	$155.90
Purchase #4	$90.99	7.205%	$97.5458	$97.55	$97.55	$97.50
Purchase #5	$46.96	11.628%	$52.4205	$52.42	$52.40	$52.40
Purchase #6	$138.50	4.625%	$144.9056	$144.91	$144.90	$144.90
Purchase #7	$220.88	3.574%	$228.7743	$228.77	$228.75	$228.80
7 purchase totals =	$914.79		$961.8573	$961.86	$961.80	$961.90