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	$168.74	11.548%	$188.2261	$188.23	$188.25	$188.20
Purchase #2	$134.77	13.709%	$153.2456	$153.25	$153.25	$153.20
Purchase #3	$210.60	5.788%	$222.7895	$222.79	$222.80	$222.80
Purchase #4	$33.71	13.710%	$38.3316	$38.33	$38.35	$38.30
Purchase #5	$246.32	9.133%	$268.8164	$268.82	$268.80	$268.80
Purchase #6	$203.55	9.413%	$222.7102	$222.71	$222.70	$222.70
Purchase #7	$180.90	6.658%	$192.9443	$192.94	$192.95	$192.90
7 purchase totals =	$1,178.59		$1,287.0637	$1,287.07	$1,287.10	$1,286.90