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	$234.73	8.588%	$254.8886	$254.89	$254.90	$254.90
Purchase #2	$86.41	4.744%	$90.5093	$90.51	$90.50	$90.50
Purchase #3	$54.48	7.774%	$58.7153	$58.72	$58.70	$58.70
Purchase #4	$18.56	8.615%	$20.1589	$20.16	$20.15	$20.20
Purchase #5	$35.42	5.483%	$37.3621	$37.36	$37.35	$37.40
Purchase #6	$83.33	11.627%	$93.0188	$93.02	$93.00	$93.00
Purchase #7	$154.88	12.812%	$174.7232	$174.72	$174.70	$174.70
7 purchase totals =	$667.81		$729.3762	$729.38	$729.30	$729.40