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	$114.80	11.391%	$127.8769	$127.88	$127.90	$127.90
Purchase #2	$92.53	13.330%	$104.8642	$104.86	$104.85	$104.90
Purchase #3	$47.39	5.293%	$49.8984	$49.90	$49.90	$49.90
Purchase #4	$25.62	5.651%	$27.0678	$27.07	$27.05	$27.10
Purchase #5	$222.78	13.818%	$253.5637	$253.56	$253.55	$253.60
Purchase #6	$245.65	11.841%	$274.7374	$274.74	$274.75	$274.70
Purchase #7	$12.69	10.473%	$14.019	$14.02	$14.00	$14.00
7 purchase totals =	$761.46		$852.0274	$852.03	$852.00	$852.10