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	$55.31	3.697%	$57.3548	$57.35	$57.35	$57.40
Purchase #2	$163.29	5.786%	$172.738	$172.74	$172.75	$172.70
Purchase #3	$196.94	7.131%	$210.9838	$210.98	$211.00	$211.00
Purchase #4	$223.38	13.252%	$252.9823	$252.98	$253.00	$253.00
Purchase #5	$223.66	6.112%	$237.3301	$237.33	$237.35	$237.30
Purchase #6	$126.96	9.850%	$139.4656	$139.47	$139.45	$139.50
Purchase #7	$51.66	9.475%	$56.5548	$56.55	$56.55	$56.60
7 purchase totals =	$1,041.20		$1,127.4094	$1,127.40	$1,127.45	$1,127.50