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	$198.26	11.161%	$220.3878	$220.39	$220.40	$220.40
Purchase #2	$73.90	6.132%	$78.4315	$78.43	$78.45	$78.40
Purchase #3	$229.50	5.803%	$242.8179	$242.82	$242.80	$242.80
Purchase #4	$157.70	11.464%	$175.7787	$175.78	$175.80	$175.80
Purchase #5	$140.48	13.532%	$159.4898	$159.49	$159.50	$159.50
Purchase #6	$75.55	6.521%	$80.4766	$80.48	$80.50	$80.50
Purchase #7	$175.40	3.839%	$182.1336	$182.13	$182.15	$182.10
7 purchase totals =	$1,050.79		$1,139.5159	$1,139.52	$1,139.60	$1,139.50