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	$156.43	11.480%	$174.3882	$174.39	$174.40	$174.40
Purchase #2	$219.53	11.546%	$244.8769	$244.88	$244.90	$244.90
Purchase #3	$224.75	4.158%	$234.0951	$234.10	$234.10	$234.10
Purchase #4	$113.26	13.461%	$128.5059	$128.51	$128.50	$128.50
Purchase #5	$87.74	3.591%	$90.8907	$90.89	$90.90	$90.90
Purchase #6	$29.78	13.497%	$33.7994	$33.80	$33.80	$33.80
Purchase #7	$64.94	10.355%	$71.6645	$71.66	$71.65	$71.70
7 purchase totals =	$896.43		$978.2207	$978.23	$978.25	$978.30