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	$56.56	4.277%	$58.9791	$58.98	$59.00	$59.00
Purchase #2	$232.59	9.643%	$255.0187	$255.02	$255.00	$255.00
Purchase #3	$189.84	5.713%	$200.6856	$200.69	$200.70	$200.70
Purchase #4	$121.44	10.163%	$133.7819	$133.78	$133.80	$133.80
Purchase #5	$53.88	11.220%	$59.9253	$59.93	$59.95	$59.90
Purchase #6	$112.58	7.406%	$120.9177	$120.92	$120.90	$120.90
Purchase #7	$100.46	6.420%	$106.9095	$106.91	$106.90	$106.90
7 purchase totals =	$867.35		$936.2178	$936.23	$936.25	$936.20