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	$111.56	10.682%	$123.4768	$123.48	$123.50	$123.50
Purchase #2	$194.86	11.106%	$216.5012	$216.50	$216.50	$216.50
Purchase #3	$88.55	7.170%	$94.899	$94.90	$94.90	$94.90
Purchase #4	$99.40	10.786%	$110.1213	$110.12	$110.10	$110.10
Purchase #5	$5.48	9.677%	$6.0103	$6.01	$6.00	$6.00
Purchase #6	$155.46	6.638%	$165.7794	$165.78	$165.80	$165.80
Purchase #7	$150.91	13.269%	$170.9342	$170.93	$170.95	$170.90
7 purchase totals =	$806.22		$887.7222	$887.72	$887.75	$887.70