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	$42.89	8.348%	$46.4705	$46.47	$46.45	$46.50
Purchase #2	$85.54	3.341%	$88.3979	$88.40	$88.40	$88.40
Purchase #3	$47.93	6.585%	$51.0862	$51.09	$51.10	$51.10
Purchase #4	$80.89	12.152%	$90.7198	$90.72	$90.70	$90.70
Purchase #5	$109.93	3.539%	$113.8204	$113.82	$113.80	$113.80
Purchase #6	$162.35	12.596%	$182.7996	$182.80	$182.80	$182.80
Purchase #7	$71.94	12.446%	$80.8937	$80.89	$80.90	$80.90
7 purchase totals =	$601.47		$654.1881	$654.19	$654.15	$654.20