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	$120.62	6.665%	$128.6593	$128.66	$128.65	$128.70
Purchase #2	$9.83	4.278%	$10.2505	$10.25	$10.25	$10.30
Purchase #3	$37.26	10.472%	$41.1619	$41.16	$41.15	$41.20
Purchase #4	$248.69	9.331%	$271.8953	$271.90	$271.90	$271.90
Purchase #5	$32.85	9.128%	$35.8485	$35.85	$35.85	$35.80
Purchase #6	$161.63	9.263%	$176.6018	$176.60	$176.60	$176.60
Purchase #7	$123.35	6.794%	$131.7304	$131.73	$131.75	$131.70
7 purchase totals =	$734.23		$796.1477	$796.15	$796.15	$796.20