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	$185.59	7.797%	$200.0605	$200.06	$200.05	$200.10
Purchase #2	$48.99	7.497%	$52.6628	$52.66	$52.65	$52.70
Purchase #3	$115.53	12.393%	$129.8476	$129.85	$129.85	$129.80
Purchase #4	$99.86	11.265%	$111.1092	$111.11	$111.10	$111.10
Purchase #5	$94.43	7.476%	$101.4896	$101.49	$101.50	$101.50
Purchase #6	$118.29	3.855%	$122.8501	$122.85	$122.85	$122.90
Purchase #7	$197.78	12.758%	$223.0128	$223.01	$223.00	$223.00
7 purchase totals =	$860.47		$941.0326	$941.03	$941.00	$941.10