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	$35.85	3.739%	$37.1904	$37.19	$37.20	$37.20
Purchase #2	$95.54	7.103%	$102.3262	$102.33	$102.35	$102.30
Purchase #3	$192.31	3.547%	$199.1312	$199.13	$199.15	$199.10
Purchase #4	$85.55	3.468%	$88.5169	$88.52	$88.50	$88.50
Purchase #5	$69.44	4.794%	$72.769	$72.77	$72.75	$72.80
Purchase #6	$211.37	5.156%	$222.2682	$222.27	$222.25	$222.30
Purchase #7	$7.27	5.400%	$7.6626	$7.66	$7.65	$7.70
7 purchase totals =	$697.33		$729.8645	$729.87	$729.85	$729.90