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	$163.61	4.861%	$171.5631	$171.56	$171.55	$171.60
Purchase #2	$97.93	4.483%	$102.3202	$102.32	$102.30	$102.30
Purchase #3	$238.45	6.865%	$254.8196	$254.82	$254.80	$254.80
Purchase #4	$113.75	11.707%	$127.0667	$127.07	$127.05	$127.10
Purchase #5	$148.58	12.510%	$167.1674	$167.17	$167.15	$167.20
Purchase #6	$138.73	5.210%	$145.9578	$145.96	$145.95	$146.00
Purchase #7	$160.52	5.558%	$169.4417	$169.44	$169.45	$169.40
7 purchase totals =	$1,061.57		$1,138.3365	$1,138.34	$1,138.25	$1,138.40