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	$94.86	13.406%	$107.5769	$107.58	$107.60	$107.60
Purchase #2	$65.37	11.322%	$72.7712	$72.77	$72.75	$72.80
Purchase #3	$172.99	9.376%	$189.2095	$189.21	$189.20	$189.20
Purchase #4	$202.78	12.607%	$228.3445	$228.34	$228.35	$228.30
Purchase #5	$111.75	10.854%	$123.8793	$123.88	$123.90	$123.90
Purchase #6	$245.85	5.480%	$259.3226	$259.32	$259.30	$259.30
Purchase #7	$26.75	3.811%	$27.7694	$27.77	$27.75	$27.80
7 purchase totals =	$920.35		$1,008.8734	$1,008.87	$1,008.85	$1,008.90