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	$33.85	5.127%	$35.5855	$35.59	$35.60	$35.60
Purchase #2	$222.43	12.361%	$249.9246	$249.92	$249.90	$249.90
Purchase #3	$54.31	10.433%	$59.9762	$59.98	$60.00	$60.00
Purchase #4	$149.74	11.160%	$166.451	$166.45	$166.45	$166.50
Purchase #5	$107.77	5.139%	$113.3083	$113.31	$113.30	$113.30
Purchase #6	$42.96	11.683%	$47.979	$47.98	$48.00	$48.00
Purchase #7	$110.96	3.443%	$114.7804	$114.78	$114.80	$114.80
7 purchase totals =	$722.02		$788.0050	$788.01	$788.05	$788.10