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	$65.45	11.478%	$72.9624	$72.96	$72.95	$73.00
Purchase #2	$16.75	9.109%	$18.2758	$18.28	$18.30	$18.30
Purchase #3	$239.59	9.176%	$261.5748	$261.57	$261.55	$261.60
Purchase #4	$145.82	9.564%	$159.7662	$159.77	$159.75	$159.80
Purchase #5	$65.93	10.454%	$72.8223	$72.82	$72.80	$72.80
Purchase #6	$52.37	8.338%	$56.7366	$56.74	$56.75	$56.70
Purchase #7	$149.77	12.769%	$168.8941	$168.89	$168.90	$168.90
7 purchase totals =	$735.68		$811.0322	$811.03	$811.00	$811.10