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	$10.46	6.522%	$11.1422	$11.14	$11.15	$11.10
Purchase #2	$157.59	9.773%	$172.9913	$172.99	$173.00	$173.00
Purchase #3	$90.59	11.400%	$100.9173	$100.92	$100.90	$100.90
Purchase #4	$161.93	7.773%	$174.5168	$174.52	$174.50	$174.50
Purchase #5	$13.34	4.287%	$13.9119	$13.91	$13.90	$13.90
Purchase #6	$153.73	5.465%	$162.1313	$162.13	$162.15	$162.10
Purchase #7	$57.44	10.322%	$63.369	$63.37	$63.35	$63.40
7 purchase totals =	$645.08		$698.9798	$698.98	$698.95	$698.90