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	$205.35	9.331%	$224.5112	$224.51	$224.50	$224.50
Purchase #2	$76.49	11.350%	$85.1716	$85.17	$85.15	$85.20
Purchase #3	$65.82	9.852%	$72.3046	$72.30	$72.30	$72.30
Purchase #4	$85.81	4.271%	$89.4749	$89.47	$89.45	$89.50
Purchase #5	$100.71	6.454%	$107.2098	$107.21	$107.20	$107.20
Purchase #6	$71.56	7.738%	$77.0973	$77.10	$77.10	$77.10
Purchase #7	$67.45	13.748%	$76.723	$76.72	$76.70	$76.70
7 purchase totals =	$673.19		$732.4924	$732.48	$732.40	$732.50