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	$158.90	10.840%	$176.1248	$176.12	$176.10	$176.10
Purchase #2	$69.49	10.106%	$76.5127	$76.51	$76.50	$76.50
Purchase #3	$235.55	6.351%	$250.5098	$250.51	$250.50	$250.50
Purchase #4	$102.79	12.680%	$115.8238	$115.82	$115.80	$115.80
Purchase #5	$171.71	6.594%	$183.0326	$183.03	$183.05	$183.00
Purchase #6	$244.27	5.645%	$258.059	$258.06	$258.05	$258.10
Purchase #7	$84.46	7.137%	$90.4879	$90.49	$90.50	$90.50
7 purchase totals =	$1,067.17		$1,150.5506	$1,150.54	$1,150.50	$1,150.50