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	$185.34	10.561%	$204.9138	$204.91	$204.90	$204.90
Purchase #2	$103.80	8.262%	$112.376	$112.38	$112.40	$112.40
Purchase #3	$56.60	4.249%	$59.0049	$59.00	$59.00	$59.00
Purchase #4	$162.31	6.444%	$172.7693	$172.77	$172.75	$172.80
Purchase #5	$244.38	10.588%	$270.255	$270.26	$270.25	$270.30
Purchase #6	$66.60	8.690%	$72.3875	$72.39	$72.40	$72.40
Purchase #7	$147.97	10.817%	$163.9759	$163.98	$164.00	$164.00
7 purchase totals =	$967.00		$1,055.6824	$1,055.69	$1,055.70	$1,055.80