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	$208.27	13.353%	$236.0803	$236.08	$236.10	$236.10
Purchase #2	$196.41	5.369%	$206.9553	$206.96	$206.95	$207.00
Purchase #3	$47.25	4.602%	$49.4244	$49.42	$49.40	$49.40
Purchase #4	$85.72	6.107%	$90.9549	$90.95	$90.95	$91.00
Purchase #5	$61.32	6.794%	$65.4861	$65.49	$65.50	$65.50
Purchase #6	$90.87	10.459%	$100.3741	$100.37	$100.35	$100.40
Purchase #7	$172.53	11.794%	$192.8782	$192.88	$192.90	$192.90
7 purchase totals =	$862.37		$942.1533	$942.15	$942.15	$942.30