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	$39.30	12.837%	$44.3449	$44.34	$44.35	$44.30
Purchase #2	$100.94	3.179%	$104.1489	$104.15	$104.15	$104.10
Purchase #3	$236.49	5.501%	$249.4993	$249.50	$249.50	$249.50
Purchase #4	$229.69	13.321%	$260.287	$260.29	$260.30	$260.30
Purchase #5	$129.79	10.872%	$143.9008	$143.90	$143.90	$143.90
Purchase #6	$211.51	3.182%	$218.2402	$218.24	$218.25	$218.20
Purchase #7	$51.51	6.437%	$54.8257	$54.83	$54.85	$54.80
7 purchase totals =	$999.23		$1,075.2468	$1,075.25	$1,075.30	$1,075.10