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	$69.96	4.124%	$72.8452	$72.85	$72.85	$72.80
Purchase #2	$11.78	6.266%	$12.5181	$12.52	$12.50	$12.50
Purchase #3	$99.64	12.185%	$111.7811	$111.78	$111.80	$111.80
Purchase #4	$192.91	10.228%	$212.6408	$212.64	$212.65	$212.60
Purchase #5	$195.75	13.535%	$222.2448	$222.24	$222.25	$222.20
Purchase #6	$86.68	3.753%	$89.9331	$89.93	$89.95	$89.90
Purchase #7	$123.63	12.551%	$139.1468	$139.15	$139.15	$139.10
7 purchase totals =	$780.35		$861.1099	$861.11	$861.15	$860.90