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	$66.38	3.137%	$68.4623	$68.46	$68.45	$68.50
Purchase #2	$7.82	9.799%	$8.5863	$8.59	$8.60	$8.60
Purchase #3	$232.52	6.470%	$247.564	$247.56	$247.55	$247.60
Purchase #4	$147.81	6.156%	$156.9092	$156.91	$156.90	$156.90
Purchase #5	$138.65	4.570%	$144.9863	$144.99	$145.00	$145.00
Purchase #6	$156.57	11.841%	$175.1095	$175.11	$175.10	$175.10
Purchase #7	$178.75	12.206%	$200.5682	$200.57	$200.55	$200.60
7 purchase totals =	$928.50		$1,002.1858	$1,002.19	$1,002.15	$1,002.30