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	$104.25	6.736%	$111.2723	$111.27	$111.25	$111.30
Purchase #2	$159.55	5.137%	$167.7461	$167.75	$167.75	$167.70
Purchase #3	$20.67	5.661%	$21.8401	$21.84	$21.85	$21.80
Purchase #4	$94.47	12.470%	$106.2504	$106.25	$106.25	$106.30
Purchase #5	$19.86	3.696%	$20.594	$20.59	$20.60	$20.60
Purchase #6	$148.93	10.431%	$164.4649	$164.46	$164.45	$164.50
Purchase #7	$227.57	3.657%	$235.8922	$235.89	$235.90	$235.90
7 purchase totals =	$775.30		$828.0600	$828.05	$828.05	$828.10