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	$106.71	4.512%	$111.5248	$111.52	$111.50	$111.50
Purchase #2	$71.29	3.574%	$73.8379	$73.84	$73.85	$73.80
Purchase #3	$194.39	11.351%	$216.4552	$216.46	$216.45	$216.50
Purchase #4	$216.65	10.233%	$238.8198	$238.82	$238.80	$238.80
Purchase #5	$242.42	11.417%	$270.0971	$270.10	$270.10	$270.10
Purchase #6	$121.47	8.510%	$131.8071	$131.81	$131.80	$131.80
Purchase #7	$232.34	8.328%	$251.6893	$251.69	$251.70	$251.70
7 purchase totals =	$1,185.27		$1,294.2312	$1,294.24	$1,294.20	$1,294.20