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	$98.34	6.482%	$104.7144	$104.71	$104.70	$104.70
Purchase #2	$104.57	6.781%	$111.6609	$111.66	$111.65	$111.70
Purchase #3	$229.79	9.121%	$250.7491	$250.75	$250.75	$250.70
Purchase #4	$181.61	6.562%	$193.5272	$193.53	$193.55	$193.50
Purchase #5	$42.98	5.577%	$45.377	$45.38	$45.40	$45.40
Purchase #6	$55.47	13.771%	$63.1088	$63.11	$63.10	$63.10
Purchase #7	$73.40	5.554%	$77.4766	$77.48	$77.50	$77.50
7 purchase totals =	$786.16		$846.6140	$846.62	$846.65	$846.60