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	$209.40	3.385%	$216.4882	$216.49	$216.50	$216.50
Purchase #2	$85.36	3.814%	$88.6156	$88.62	$88.60	$88.60
Purchase #3	$58.29	12.219%	$65.4125	$65.41	$65.40	$65.40
Purchase #4	$88.33	13.844%	$100.5584	$100.56	$100.55	$100.60
Purchase #5	$108.28	5.388%	$114.1141	$114.11	$114.10	$114.10
Purchase #6	$198.89	11.453%	$221.6689	$221.67	$221.65	$221.70
Purchase #7	$182.47	12.637%	$205.5287	$205.53	$205.55	$205.50
7 purchase totals =	$931.02		$1,012.3864	$1,012.39	$1,012.35	$1,012.40