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	$190.58	3.162%	$196.6061	$196.61	$196.60	$196.60
Purchase #2	$151.89	9.142%	$165.7758	$165.78	$165.80	$165.80
Purchase #3	$75.36	13.667%	$85.6595	$85.66	$85.65	$85.70
Purchase #4	$157.73	4.284%	$164.4872	$164.49	$164.50	$164.50
Purchase #5	$185.88	6.311%	$197.6109	$197.61	$197.60	$197.60
Purchase #6	$35.80	10.566%	$39.5826	$39.58	$39.60	$39.60
Purchase #7	$227.58	6.346%	$242.0222	$242.02	$242.00	$242.00
7 purchase totals =	$1,024.82		$1,091.7443	$1,091.75	$1,091.75	$1,091.80