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	$195.57	10.376%	$215.8623	$215.86	$215.85	$215.90
Purchase #2	$214.60	3.455%	$222.0144	$222.01	$222.00	$222.00
Purchase #3	$78.33	4.172%	$81.5979	$81.60	$81.60	$81.60
Purchase #4	$183.26	3.478%	$189.6338	$189.63	$189.65	$189.60
Purchase #5	$88.96	13.102%	$100.6155	$100.62	$100.60	$100.60
Purchase #6	$34.98	6.764%	$37.346	$37.35	$37.35	$37.30
Purchase #7	$49.59	8.220%	$53.6663	$53.67	$53.65	$53.70
7 purchase totals =	$845.29		$900.7362	$900.74	$900.70	$900.70