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	$226.55	5.145%	$238.206	$238.21	$238.20	$238.20
Purchase #2	$79.98	13.504%	$90.7805	$90.78	$90.80	$90.80
Purchase #3	$181.81	8.134%	$196.5984	$196.60	$196.60	$196.60
Purchase #4	$162.35	5.261%	$170.8912	$170.89	$170.90	$170.90
Purchase #5	$131.82	10.107%	$145.143	$145.14	$145.15	$145.10
Purchase #6	$27.69	6.206%	$29.4084	$29.41	$29.40	$29.40
Purchase #7	$145.26	6.412%	$154.5741	$154.57	$154.55	$154.60
7 purchase totals =	$955.46		$1,025.6016	$1,025.60	$1,025.60	$1,025.60