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	$98.50	4.685%	$103.1147	$103.11	$103.10	$103.10
Purchase #2	$13.94	11.154%	$15.4949	$15.49	$15.50	$15.50
Purchase #3	$46.32	4.459%	$48.3854	$48.39	$48.40	$48.40
Purchase #4	$32.52	10.362%	$35.8897	$35.89	$35.90	$35.90
Purchase #5	$108.32	11.864%	$121.1711	$121.17	$121.15	$121.20
Purchase #6	$77.83	3.707%	$80.7152	$80.72	$80.70	$80.70
Purchase #7	$155.43	9.138%	$169.6332	$169.63	$169.65	$169.60
7 purchase totals =	$532.86		$574.4042	$574.40	$574.40	$574.40