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	$129.50	3.688%	$134.276	$134.28	$134.30	$134.30
Purchase #2	$234.60	9.476%	$256.8307	$256.83	$256.85	$256.80
Purchase #3	$78.42	10.819%	$86.9043	$86.90	$86.90	$86.90
Purchase #4	$48.32	12.740%	$54.476	$54.48	$54.50	$54.50
Purchase #5	$148.81	9.491%	$162.9336	$162.93	$162.95	$162.90
Purchase #6	$156.76	12.103%	$175.7327	$175.73	$175.75	$175.70
Purchase #7	$49.59	11.438%	$55.2621	$55.26	$55.25	$55.30
7 purchase totals =	$846.00		$926.4154	$926.41	$926.50	$926.40