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	$110.56	6.342%	$117.5717	$117.57	$117.55	$117.60
Purchase #2	$59.93	11.425%	$66.777	$66.78	$66.80	$66.80
Purchase #3	$8.34	6.701%	$8.8989	$8.90	$8.90	$8.90
Purchase #4	$244.61	10.137%	$269.4061	$269.41	$269.40	$269.40
Purchase #5	$174.98	12.310%	$196.52	$196.52	$196.50	$196.50
Purchase #6	$142.72	12.206%	$160.1404	$160.14	$160.15	$160.10
Purchase #7	$81.86	6.542%	$87.2153	$87.22	$87.20	$87.20
7 purchase totals =	$823.00		$906.5294	$906.54	$906.50	$906.50