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	$192.55	5.590%	$203.3135	$203.31	$203.30	$203.30
Purchase #2	$19.59	11.542%	$21.8511	$21.85	$21.85	$21.90
Purchase #3	$25.58	3.763%	$26.5426	$26.54	$26.55	$26.50
Purchase #4	$99.43	10.394%	$109.7648	$109.76	$109.75	$109.80
Purchase #5	$71.54	9.674%	$78.4608	$78.46	$78.45	$78.50
Purchase #6	$241.29	11.621%	$269.3303	$269.33	$269.35	$269.30
Purchase #7	$137.67	10.414%	$152.007	$152.01	$152.00	$152.00
7 purchase totals =	$787.65		$861.2701	$861.26	$861.25	$861.30