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	$34.36	8.161%	$37.1641	$37.16	$37.15	$37.20
Purchase #2	$92.80	12.858%	$104.7322	$104.73	$104.75	$104.70
Purchase #3	$133.50	4.200%	$139.107	$139.11	$139.10	$139.10
Purchase #4	$160.95	10.734%	$178.2264	$178.23	$178.25	$178.20
Purchase #5	$96.79	3.578%	$100.2531	$100.25	$100.25	$100.30
Purchase #6	$56.69	6.495%	$60.372	$60.37	$60.35	$60.40
Purchase #7	$124.83	13.567%	$141.7657	$141.77	$141.75	$141.80
7 purchase totals =	$699.92		$761.6205	$761.62	$761.60	$761.70