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	$34.83	11.411%	$38.8045	$38.80	$38.80	$38.80
Purchase #2	$173.62	9.720%	$190.4959	$190.50	$190.50	$190.50
Purchase #3	$247.51	11.293%	$275.4613	$275.46	$275.45	$275.50
Purchase #4	$21.85	4.231%	$22.7745	$22.77	$22.75	$22.80
Purchase #5	$224.28	3.693%	$232.5627	$232.56	$232.55	$232.60
Purchase #6	$41.76	9.802%	$45.8533	$45.85	$45.85	$45.90
Purchase #7	$240.73	5.470%	$253.8979	$253.90	$253.90	$253.90
7 purchase totals =	$984.58		$1,059.8501	$1,059.84	$1,059.80	$1,060.00