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	$172.78	13.847%	$196.7048	$196.70	$196.70	$196.70
Purchase #2	$248.90	12.463%	$279.9204	$279.92	$279.90	$279.90
Purchase #3	$103.86	5.475%	$109.5463	$109.55	$109.55	$109.50
Purchase #4	$126.38	7.801%	$136.2389	$136.24	$136.25	$136.20
Purchase #5	$35.42	13.505%	$40.2035	$40.20	$40.20	$40.20
Purchase #6	$211.64	6.186%	$224.7321	$224.73	$224.75	$224.70
Purchase #7	$67.28	11.668%	$75.1302	$75.13	$75.15	$75.10
7 purchase totals =	$966.26		$1,062.4762	$1,062.47	$1,062.50	$1,062.30