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	$181.29	13.587%	$205.9219	$205.92	$205.90	$205.90
Purchase #2	$229.55	13.416%	$260.3464	$260.35	$260.35	$260.30
Purchase #3	$94.63	6.688%	$100.9589	$100.96	$100.95	$101.00
Purchase #4	$68.44	4.796%	$71.7224	$71.72	$71.70	$71.70
Purchase #5	$242.40	5.311%	$255.2739	$255.27	$255.25	$255.30
Purchase #6	$47.99	11.639%	$53.5756	$53.58	$53.60	$53.60
Purchase #7	$63.80	12.840%	$71.9919	$71.99	$72.00	$72.00
7 purchase totals =	$928.10		$1,019.7910	$1,019.79	$1,019.75	$1,019.80