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	$105.47	10.134%	$116.1583	$116.16	$116.15	$116.20
Purchase #2	$27.34	5.221%	$28.7674	$28.77	$28.75	$28.80
Purchase #3	$87.39	6.752%	$93.2906	$93.29	$93.30	$93.30
Purchase #4	$99.44	6.156%	$105.5615	$105.56	$105.55	$105.60
Purchase #5	$51.75	12.794%	$58.3709	$58.37	$58.35	$58.40
Purchase #6	$210.36	5.606%	$222.1528	$222.15	$222.15	$222.20
Purchase #7	$107.44	3.565%	$111.2702	$111.27	$111.25	$111.30
7 purchase totals =	$689.19		$735.5717	$735.57	$735.50	$735.80