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	$41.28	12.518%	$46.4474	$46.45	$46.45	$46.40
Purchase #2	$124.48	5.858%	$131.772	$131.77	$131.75	$131.80
Purchase #3	$127.58	6.847%	$136.3154	$136.32	$136.30	$136.30
Purchase #4	$48.88	3.263%	$50.475	$50.48	$50.50	$50.50
Purchase #5	$120.70	4.760%	$126.4453	$126.45	$126.45	$126.40
Purchase #6	$112.35	12.571%	$126.4735	$126.47	$126.45	$126.50
Purchase #7	$65.45	4.744%	$68.5549	$68.55	$68.55	$68.60
7 purchase totals =	$640.72		$686.4835	$686.49	$686.45	$686.50