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	$177.29	10.143%	$195.2725	$195.27	$195.25	$195.30
Purchase #2	$150.31	12.367%	$168.8988	$168.90	$168.90	$168.90
Purchase #3	$115.83	7.805%	$124.8705	$124.87	$124.85	$124.90
Purchase #4	$29.36	3.773%	$30.4678	$30.47	$30.45	$30.50
Purchase #5	$209.84	13.613%	$238.4055	$238.41	$238.40	$238.40
Purchase #6	$164.76	4.294%	$171.8348	$171.83	$171.85	$171.80
Purchase #7	$172.41	9.128%	$188.1476	$188.15	$188.15	$188.10
7 purchase totals =	$1,019.80		$1,117.8975	$1,117.90	$1,117.85	$1,117.90