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	$59.67	3.473%	$61.7423	$61.74	$61.75	$61.70
Purchase #2	$247.98	12.769%	$279.6446	$279.64	$279.65	$279.60
Purchase #3	$136.83	5.334%	$144.1285	$144.13	$144.15	$144.10
Purchase #4	$40.84	6.299%	$43.4125	$43.41	$43.40	$43.40
Purchase #5	$159.37	5.519%	$168.1656	$168.17	$168.15	$168.20
Purchase #6	$248.77	8.199%	$269.1667	$269.17	$269.15	$269.20
Purchase #7	$32.55	4.118%	$33.8904	$33.89	$33.90	$33.90
7 purchase totals =	$926.01		$1,000.1506	$1,000.15	$1,000.15	$1,000.10