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	$104.68	4.105%	$108.9771	$108.98	$109.00	$109.00
Purchase #2	$101.86	12.460%	$114.5518	$114.55	$114.55	$114.60
Purchase #3	$95.56	4.112%	$99.4894	$99.49	$99.50	$99.50
Purchase #4	$88.61	10.389%	$97.8157	$97.82	$97.80	$97.80
Purchase #5	$82.35	6.721%	$87.8847	$87.88	$87.90	$87.90
Purchase #6	$244.45	3.636%	$253.3382	$253.34	$253.35	$253.30
Purchase #7	$149.60	12.474%	$168.2611	$168.26	$168.25	$168.30
7 purchase totals =	$867.11		$930.3180	$930.32	$930.35	$930.40