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	$112.61	12.850%	$127.0804	$127.08	$127.10	$127.10
Purchase #2	$126.37	11.691%	$141.1439	$141.14	$141.15	$141.10
Purchase #3	$108.31	11.245%	$120.4895	$120.49	$120.50	$120.50
Purchase #4	$56.34	11.532%	$62.8371	$62.84	$62.85	$62.80
Purchase #5	$32.33	10.542%	$35.7382	$35.74	$35.75	$35.70
Purchase #6	$90.58	8.686%	$98.4478	$98.45	$98.45	$98.40
Purchase #7	$120.79	5.413%	$127.3284	$127.33	$127.35	$127.30
7 purchase totals =	$647.33		$713.0653	$713.07	$713.15	$712.90