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	$150.57	5.167%	$158.35	$158.35	$158.35	$158.40
Purchase #2	$216.95	8.269%	$234.8896	$234.89	$234.90	$234.90
Purchase #3	$223.86	7.464%	$240.5689	$240.57	$240.55	$240.60
Purchase #4	$86.32	13.196%	$97.7108	$97.71	$97.70	$97.70
Purchase #5	$179.94	3.297%	$185.8726	$185.87	$185.85	$185.90
Purchase #6	$197.61	9.369%	$216.1241	$216.12	$216.10	$216.10
Purchase #7	$36.61	10.350%	$40.3991	$40.40	$40.40	$40.40
7 purchase totals =	$1,091.86		$1,173.9151	$1,173.91	$1,173.85	$1,174.00