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	$89.32	6.393%	$95.0302	$95.03	$95.05	$95.00
Purchase #2	$220.38	3.726%	$228.5914	$228.59	$228.60	$228.60
Purchase #3	$146.73	3.488%	$151.8479	$151.85	$151.85	$151.80
Purchase #4	$80.80	12.427%	$90.841	$90.84	$90.85	$90.80
Purchase #5	$111.44	4.167%	$116.0837	$116.08	$116.10	$116.10
Purchase #6	$249.37	9.820%	$273.8581	$273.86	$273.85	$273.90
Purchase #7	$67.57	5.443%	$71.2478	$71.25	$71.25	$71.20
7 purchase totals =	$965.61		$1,027.5001	$1,027.50	$1,027.55	$1,027.40