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	$105.28	5.739%	$111.322	$111.32	$111.30	$111.30
Purchase #2	$81.62	6.214%	$86.6919	$86.69	$86.70	$86.70
Purchase #3	$113.29	13.558%	$128.6499	$128.65	$128.65	$128.60
Purchase #4	$90.77	10.237%	$100.0621	$100.06	$100.05	$100.10
Purchase #5	$176.74	10.219%	$194.8011	$194.80	$194.80	$194.80
Purchase #6	$61.73	6.627%	$65.8208	$65.82	$65.80	$65.80
Purchase #7	$175.90	12.130%	$197.2367	$197.24	$197.25	$197.20
7 purchase totals =	$805.33		$884.5845	$884.58	$884.55	$884.50