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	$58.30	9.596%	$63.8945	$63.89	$63.90	$63.90
Purchase #2	$80.77	5.518%	$85.2269	$85.23	$85.25	$85.20
Purchase #3	$58.45	11.249%	$65.025	$65.03	$65.05	$65.00
Purchase #4	$218.70	9.225%	$238.8751	$238.88	$238.90	$238.90
Purchase #5	$211.39	13.611%	$240.1623	$240.16	$240.15	$240.20
Purchase #6	$26.27	3.260%	$27.1264	$27.13	$27.15	$27.10
Purchase #7	$144.44	10.857%	$160.1219	$160.12	$160.10	$160.10
7 purchase totals =	$798.32		$880.4321	$880.44	$880.50	$880.40