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	$225.99	12.860%	$255.0523	$255.05	$255.05	$255.10
Purchase #2	$210.96	5.585%	$222.7421	$222.74	$222.75	$222.70
Purchase #3	$39.75	11.175%	$44.1921	$44.19	$44.20	$44.20
Purchase #4	$36.56	13.768%	$41.5936	$41.59	$41.60	$41.60
Purchase #5	$101.92	11.327%	$113.4645	$113.46	$113.45	$113.50
Purchase #6	$220.56	12.320%	$247.733	$247.73	$247.75	$247.70
Purchase #7	$84.41	7.405%	$90.6606	$90.66	$90.65	$90.70
7 purchase totals =	$920.15		$1,015.4382	$1,015.42	$1,015.45	$1,015.50