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	$42.91	5.869%	$45.4284	$45.43	$45.45	$45.40
Purchase #2	$223.69	9.104%	$244.0547	$244.05	$244.05	$244.10
Purchase #3	$89.27	13.536%	$101.3536	$101.35	$101.35	$101.40
Purchase #4	$201.54	4.759%	$211.1313	$211.13	$211.15	$211.10
Purchase #5	$201.48	5.137%	$211.83	$211.83	$211.85	$211.80
Purchase #6	$30.51	4.666%	$31.9336	$31.93	$31.95	$31.90
Purchase #7	$142.52	13.554%	$161.8372	$161.84	$161.85	$161.80
7 purchase totals =	$931.92		$1,007.5688	$1,007.56	$1,007.65	$1,007.50