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	$128.92	12.546%	$145.0943	$145.09	$145.10	$145.10
Purchase #2	$201.58	3.791%	$209.2219	$209.22	$209.20	$209.20
Purchase #3	$64.55	10.411%	$71.2703	$71.27	$71.25	$71.30
Purchase #4	$81.50	12.400%	$91.606	$91.61	$91.60	$91.60
Purchase #5	$10.80	6.489%	$11.5008	$11.50	$11.50	$11.50
Purchase #6	$25.81	10.510%	$28.5226	$28.52	$28.50	$28.50
Purchase #7	$114.32	8.349%	$123.8646	$123.86	$123.85	$123.90
7 purchase totals =	$627.48		$681.0805	$681.07	$681.00	$681.10