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	$163.52	4.665%	$171.1482	$171.15	$171.15	$171.10
Purchase #2	$61.77	5.541%	$65.1927	$65.19	$65.20	$65.20
Purchase #3	$206.40	9.861%	$226.7531	$226.75	$226.75	$226.80
Purchase #4	$52.55	12.552%	$59.1461	$59.15	$59.15	$59.10
Purchase #5	$200.43	10.525%	$221.5253	$221.53	$221.55	$221.50
Purchase #6	$10.39	8.181%	$11.24	$11.24	$11.25	$11.20
Purchase #7	$10.81	4.405%	$11.2862	$11.29	$11.30	$11.30
7 purchase totals =	$705.87		$766.2916	$766.30	$766.35	$766.20