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	$127.88	13.180%	$144.7346	$144.73	$144.75	$144.70
Purchase #2	$92.81	7.372%	$99.652	$99.65	$99.65	$99.70
Purchase #3	$19.47	8.369%	$21.0994	$21.10	$21.10	$21.10
Purchase #4	$246.36	11.652%	$275.0659	$275.07	$275.05	$275.10
Purchase #5	$116.77	9.293%	$127.6214	$127.62	$127.60	$127.60
Purchase #6	$233.25	4.435%	$243.5946	$243.59	$243.60	$243.60
Purchase #7	$218.25	9.132%	$238.1806	$238.18	$238.20	$238.20
7 purchase totals =	$1,054.79		$1,149.9485	$1,149.94	$1,149.95	$1,150.00