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	$224.47	8.193%	$242.8608	$242.86	$242.85	$242.90
Purchase #2	$123.37	4.705%	$129.1746	$129.17	$129.15	$129.20
Purchase #3	$44.55	4.839%	$46.7058	$46.71	$46.70	$46.70
Purchase #4	$181.76	4.308%	$189.5902	$189.59	$189.60	$189.60
Purchase #5	$90.35	10.715%	$100.031	$100.03	$100.05	$100.00
Purchase #6	$41.39	11.869%	$46.3026	$46.30	$46.30	$46.30
Purchase #7	$32.78	8.633%	$35.6099	$35.61	$35.60	$35.60
7 purchase totals =	$738.67		$790.2749	$790.27	$790.25	$790.30