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	$130.86	8.178%	$141.5617	$141.56	$141.55	$141.60
Purchase #2	$59.72	12.588%	$67.2376	$67.24	$67.25	$67.20
Purchase #3	$239.79	5.462%	$252.8873	$252.89	$252.90	$252.90
Purchase #4	$187.40	5.779%	$198.2298	$198.23	$198.25	$198.20
Purchase #5	$207.78	4.156%	$216.4153	$216.42	$216.40	$216.40
Purchase #6	$66.37	8.221%	$71.8263	$71.83	$71.85	$71.80
Purchase #7	$219.34	9.585%	$240.3637	$240.36	$240.35	$240.40
7 purchase totals =	$1,111.26		$1,188.5217	$1,188.53	$1,188.55	$1,188.50