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	$209.25	4.107%	$217.8439	$217.84	$217.85	$217.80
Purchase #2	$110.51	12.792%	$124.6464	$124.65	$124.65	$124.60
Purchase #3	$108.60	4.688%	$113.6912	$113.69	$113.70	$113.70
Purchase #4	$72.42	8.424%	$78.5207	$78.52	$78.50	$78.50
Purchase #5	$55.59	7.468%	$59.7415	$59.74	$59.75	$59.70
Purchase #6	$48.93	6.805%	$52.2597	$52.26	$52.25	$52.30
Purchase #7	$152.25	6.423%	$162.029	$162.03	$162.05	$162.00
7 purchase totals =	$757.55		$808.7324	$808.73	$808.75	$808.60