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	$141.90	13.490%	$161.0423	$161.04	$161.05	$161.00
Purchase #2	$211.46	11.206%	$235.1562	$235.16	$235.15	$235.20
Purchase #3	$69.36	9.323%	$75.8264	$75.83	$75.85	$75.80
Purchase #4	$123.29	3.230%	$127.2723	$127.27	$127.25	$127.30
Purchase #5	$117.52	12.216%	$131.8762	$131.88	$131.90	$131.90
Purchase #6	$48.43	11.788%	$54.1389	$54.14	$54.15	$54.10
Purchase #7	$160.52	7.600%	$172.7195	$172.72	$172.70	$172.70
7 purchase totals =	$872.48		$958.0318	$958.04	$958.05	$958.00