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	$212.90	10.399%	$235.0395	$235.04	$235.05	$235.00
Purchase #2	$87.53	3.667%	$90.7397	$90.74	$90.75	$90.70
Purchase #3	$109.73	8.798%	$119.384	$119.38	$119.40	$119.40
Purchase #4	$228.92	11.612%	$255.5022	$255.50	$255.50	$255.50
Purchase #5	$24.48	3.113%	$25.2421	$25.24	$25.25	$25.20
Purchase #6	$99.52	8.694%	$108.1723	$108.17	$108.15	$108.20
Purchase #7	$80.96	10.126%	$89.158	$89.16	$89.15	$89.20
7 purchase totals =	$844.04		$923.2378	$923.23	$923.25	$923.20