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	$172.96	7.741%	$186.3488	$186.35	$186.35	$186.30
Purchase #2	$29.49	5.686%	$31.1668	$31.17	$31.15	$31.20
Purchase #3	$100.95	10.754%	$111.8062	$111.81	$111.80	$111.80
Purchase #4	$56.39	4.848%	$59.1238	$59.12	$59.10	$59.10
Purchase #5	$79.66	6.426%	$84.779	$84.78	$84.80	$84.80
Purchase #6	$127.64	11.255%	$142.0059	$142.01	$142.00	$142.00
Purchase #7	$184.45	4.616%	$192.9642	$192.96	$192.95	$193.00
7 purchase totals =	$751.54		$808.1947	$808.20	$808.15	$808.20