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	$31.62	11.419%	$35.2307	$35.23	$35.25	$35.20
Purchase #2	$232.94	4.362%	$243.1008	$243.10	$243.10	$243.10
Purchase #3	$94.36	8.525%	$102.4042	$102.40	$102.40	$102.40
Purchase #4	$70.44	10.769%	$78.0257	$78.03	$78.05	$78.00
Purchase #5	$42.42	7.856%	$45.7525	$45.75	$45.75	$45.80
Purchase #6	$100.64	11.866%	$112.5819	$112.58	$112.60	$112.60
Purchase #7	$146.46	4.254%	$152.6904	$152.69	$152.70	$152.70
7 purchase totals =	$718.88		$769.7862	$769.78	$769.85	$769.80