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	$43.74	4.291%	$45.6169	$45.62	$45.60	$45.60
Purchase #2	$230.27	11.435%	$256.6014	$256.60	$256.60	$256.60
Purchase #3	$159.91	4.749%	$167.5041	$167.50	$167.50	$167.50
Purchase #4	$33.80	6.108%	$35.8645	$35.86	$35.85	$35.90
Purchase #5	$33.40	5.384%	$35.1983	$35.20	$35.20	$35.20
Purchase #6	$80.42	11.487%	$89.6578	$89.66	$89.65	$89.70
Purchase #7	$225.95	9.581%	$247.5983	$247.60	$247.60	$247.60
7 purchase totals =	$807.49		$878.0413	$878.04	$878.00	$878.10