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	$141.67	13.115%	$160.25	$160.25	$160.25	$160.30
Purchase #2	$237.29	13.736%	$269.8842	$269.88	$269.90	$269.90
Purchase #3	$203.34	3.842%	$211.1523	$211.15	$211.15	$211.20
Purchase #4	$129.93	7.840%	$140.1165	$140.12	$140.10	$140.10
Purchase #5	$83.54	10.531%	$92.3376	$92.34	$92.35	$92.30
Purchase #6	$185.82	5.785%	$196.5697	$196.57	$196.55	$196.60
Purchase #7	$118.77	4.152%	$123.7013	$123.70	$123.70	$123.70
7 purchase totals =	$1,100.36		$1,194.0116	$1,194.01	$1,194.00	$1,194.10