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	$93.35	10.372%	$103.0323	$103.03	$103.05	$103.00
Purchase #2	$188.38	11.555%	$210.1473	$210.15	$210.15	$210.10
Purchase #3	$117.73	5.230%	$123.8873	$123.89	$123.90	$123.90
Purchase #4	$55.41	13.710%	$63.0067	$63.01	$63.00	$63.00
Purchase #5	$173.61	8.543%	$188.4415	$188.44	$188.45	$188.40
Purchase #6	$90.29	4.592%	$94.4361	$94.44	$94.45	$94.40
Purchase #7	$246.31	3.836%	$255.7585	$255.76	$255.75	$255.80
7 purchase totals =	$965.08		$1,038.7097	$1,038.72	$1,038.75	$1,038.60