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	$212.31	4.746%	$222.3862	$222.39	$222.40	$222.40
Purchase #2	$80.76	3.116%	$83.2765	$83.28	$83.30	$83.30
Purchase #3	$79.75	3.342%	$82.4152	$82.42	$82.40	$82.40
Purchase #4	$5.75	9.415%	$6.2914	$6.29	$6.30	$6.30
Purchase #5	$115.67	12.393%	$130.005	$130.01	$130.00	$130.00
Purchase #6	$185.51	8.236%	$200.7886	$200.79	$200.80	$200.80
Purchase #7	$13.86	9.548%	$15.1834	$15.18	$15.20	$15.20
7 purchase totals =	$693.61		$740.3463	$740.36	$740.40	$740.40