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	$56.83	7.722%	$61.2184	$61.22	$61.20	$61.20
Purchase #2	$69.61	4.794%	$72.9471	$72.95	$72.95	$72.90
Purchase #3	$116.88	10.477%	$129.1255	$129.13	$129.15	$129.10
Purchase #4	$100.61	4.821%	$105.4604	$105.46	$105.45	$105.50
Purchase #5	$247.50	11.127%	$275.0393	$275.04	$275.05	$275.00
Purchase #6	$241.87	5.471%	$255.1027	$255.10	$255.10	$255.10
Purchase #7	$197.94	12.871%	$223.4169	$223.42	$223.40	$223.40
7 purchase totals =	$1,031.24		$1,122.3103	$1,122.32	$1,122.30	$1,122.20