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	$118.50	7.518%	$127.4088	$127.41	$127.40	$127.40
Purchase #2	$230.79	3.380%	$238.5907	$238.59	$238.60	$238.60
Purchase #3	$98.48	8.527%	$106.8774	$106.88	$106.90	$106.90
Purchase #4	$42.32	3.831%	$43.9413	$43.94	$43.95	$43.90
Purchase #5	$207.82	8.319%	$225.1085	$225.11	$225.10	$225.10
Purchase #6	$69.58	12.436%	$78.233	$78.23	$78.25	$78.20
Purchase #7	$115.36	5.539%	$121.7498	$121.75	$121.75	$121.70
7 purchase totals =	$882.85		$941.9095	$941.91	$941.95	$941.80