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	$131.35	9.580%	$143.9333	$143.93	$143.95	$143.90
Purchase #2	$198.57	8.280%	$215.0116	$215.01	$215.00	$215.00
Purchase #3	$12.81	10.637%	$14.1726	$14.17	$14.15	$14.20
Purchase #4	$115.33	10.137%	$127.021	$127.02	$127.00	$127.00
Purchase #5	$41.89	8.848%	$45.5964	$45.60	$45.60	$45.60
Purchase #6	$159.38	13.226%	$180.4596	$180.46	$180.45	$180.50
Purchase #7	$250.76	8.781%	$272.7792	$272.78	$272.80	$272.80
7 purchase totals =	$910.09		$998.9737	$998.97	$998.95	$999.00