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	$117.31	5.578%	$123.8536	$123.85	$123.85	$123.90
Purchase #2	$91.55	13.434%	$103.8488	$103.85	$103.85	$103.80
Purchase #3	$155.97	9.654%	$171.0273	$171.03	$171.05	$171.00
Purchase #4	$134.62	4.822%	$141.1114	$141.11	$141.10	$141.10
Purchase #5	$136.72	10.604%	$151.2178	$151.22	$151.20	$151.20
Purchase #6	$10.57	6.807%	$11.2895	$11.29	$11.30	$11.30
Purchase #7	$187.76	11.449%	$209.2566	$209.26	$209.25	$209.30
7 purchase totals =	$834.50		$911.6050	$911.61	$911.60	$911.60