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	$221.98	3.833%	$230.4885	$230.49	$230.50	$230.50
Purchase #2	$46.79	3.121%	$48.2503	$48.25	$48.25	$48.30
Purchase #3	$81.90	9.442%	$89.633	$89.63	$89.65	$89.60
Purchase #4	$196.41	5.245%	$206.7117	$206.71	$206.70	$206.70
Purchase #5	$83.84	7.155%	$89.8388	$89.84	$89.85	$89.80
Purchase #6	$19.29	4.706%	$20.1978	$20.20	$20.20	$20.20
Purchase #7	$169.27	3.481%	$175.1623	$175.16	$175.15	$175.20
7 purchase totals =	$819.48		$860.2824	$860.28	$860.30	$860.30