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	$151.41	8.671%	$164.5388	$164.54	$164.55	$164.50
Purchase #2	$20.37	5.370%	$21.4639	$21.46	$21.45	$21.50
Purchase #3	$243.29	11.650%	$271.6333	$271.63	$271.65	$271.60
Purchase #4	$150.44	3.590%	$155.8408	$155.84	$155.85	$155.80
Purchase #5	$226.89	10.206%	$250.0464	$250.05	$250.05	$250.00
Purchase #6	$59.37	3.611%	$61.5139	$61.51	$61.50	$61.50
Purchase #7	$84.65	3.175%	$87.3376	$87.34	$87.35	$87.30
7 purchase totals =	$936.42		$1,012.3747	$1,012.37	$1,012.40	$1,012.20