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	$148.64	12.316%	$166.9465	$166.95	$166.95	$166.90
Purchase #2	$85.76	5.341%	$90.3404	$90.34	$90.35	$90.30
Purchase #3	$143.78	8.327%	$155.7526	$155.75	$155.75	$155.80
Purchase #4	$29.31	9.218%	$32.0118	$32.01	$32.00	$32.00
Purchase #5	$79.77	11.765%	$89.1549	$89.15	$89.15	$89.20
Purchase #6	$173.91	12.121%	$194.9896	$194.99	$195.00	$195.00
Purchase #7	$141.88	10.299%	$156.4922	$156.49	$156.50	$156.50
7 purchase totals =	$803.05		$885.6880	$885.68	$885.70	$885.70