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	$175.48	3.685%	$181.9464	$181.95	$181.95	$181.90
Purchase #2	$91.55	4.493%	$95.6633	$95.66	$95.65	$95.70
Purchase #3	$36.74	7.698%	$39.5682	$39.57	$39.55	$39.60
Purchase #4	$109.81	12.544%	$123.5846	$123.58	$123.60	$123.60
Purchase #5	$250.87	6.216%	$266.4641	$266.46	$266.45	$266.50
Purchase #6	$97.98	6.304%	$104.1567	$104.16	$104.15	$104.20
Purchase #7	$233.64	6.772%	$249.4621	$249.46	$249.45	$249.50
7 purchase totals =	$996.07		$1,060.8454	$1,060.84	$1,060.80	$1,061.00