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	$43.84	9.451%	$47.9833	$47.98	$48.00	$48.00
Purchase #2	$194.57	10.745%	$215.4765	$215.48	$215.50	$215.50
Purchase #3	$20.25	8.314%	$21.9336	$21.93	$21.95	$21.90
Purchase #4	$219.87	9.839%	$241.503	$241.50	$241.50	$241.50
Purchase #5	$53.98	9.733%	$59.2339	$59.23	$59.25	$59.20
Purchase #6	$195.54	7.805%	$210.8019	$210.80	$210.80	$210.80
Purchase #7	$92.93	7.306%	$99.7195	$99.72	$99.70	$99.70
7 purchase totals =	$820.98		$896.6517	$896.64	$896.70	$896.60