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	$93.30	3.111%	$96.2026	$96.20	$96.20	$96.20
Purchase #2	$159.95	5.588%	$168.888	$168.89	$168.90	$168.90
Purchase #3	$161.80	6.829%	$172.8493	$172.85	$172.85	$172.80
Purchase #4	$99.43	3.361%	$102.7718	$102.77	$102.75	$102.80
Purchase #5	$48.74	4.573%	$50.9689	$50.97	$50.95	$51.00
Purchase #6	$89.90	10.129%	$99.006	$99.01	$99.00	$99.00
Purchase #7	$33.37	5.695%	$35.2704	$35.27	$35.25	$35.30
7 purchase totals =	$686.49		$725.9570	$725.96	$725.90	$726.00