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	$46.78	13.587%	$53.136	$53.14	$53.15	$53.10
Purchase #2	$72.63	11.483%	$80.9701	$80.97	$80.95	$81.00
Purchase #3	$209.47	4.307%	$218.4919	$218.49	$218.50	$218.50
Purchase #4	$179.62	6.303%	$190.9414	$190.94	$190.95	$190.90
Purchase #5	$218.77	4.807%	$229.2863	$229.29	$229.30	$229.30
Purchase #6	$160.38	3.292%	$165.6597	$165.66	$165.65	$165.70
Purchase #7	$142.94	5.634%	$150.9932	$150.99	$151.00	$151.00
7 purchase totals =	$1,030.59		$1,089.4786	$1,089.48	$1,089.50	$1,089.50