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	$150.25	7.585%	$161.6465	$161.65	$161.65	$161.60
Purchase #2	$176.57	13.720%	$200.7954	$200.80	$200.80	$200.80
Purchase #3	$89.53	11.562%	$99.8815	$99.88	$99.90	$99.90
Purchase #4	$116.45	13.276%	$131.9099	$131.91	$131.90	$131.90
Purchase #5	$28.67	4.332%	$29.912	$29.91	$29.90	$29.90
Purchase #6	$215.41	3.771%	$223.5331	$223.53	$223.55	$223.50
Purchase #7	$23.35	10.646%	$25.8358	$25.84	$25.85	$25.80
7 purchase totals =	$800.23		$873.5142	$873.52	$873.55	$873.40