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	$17.53	9.772%	$19.243	$19.24	$19.25	$19.20
Purchase #2	$124.88	13.319%	$141.5128	$141.51	$141.50	$141.50
Purchase #3	$51.90	4.557%	$54.2651	$54.27	$54.25	$54.30
Purchase #4	$27.93	13.559%	$31.717	$31.72	$31.70	$31.70
Purchase #5	$192.49	13.377%	$218.2394	$218.24	$218.25	$218.20
Purchase #6	$168.37	9.220%	$183.8937	$183.89	$183.90	$183.90
Purchase #7	$215.49	3.398%	$222.8124	$222.81	$222.80	$222.80
7 purchase totals =	$798.59		$871.6834	$871.68	$871.65	$871.60