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	$70.86	3.530%	$73.3614	$73.36	$73.35	$73.40
Purchase #2	$214.80	11.315%	$239.1046	$239.10	$239.10	$239.10
Purchase #3	$210.72	10.795%	$233.4672	$233.47	$233.45	$233.50
Purchase #4	$176.44	6.810%	$188.4556	$188.46	$188.45	$188.50
Purchase #5	$206.58	8.134%	$223.3832	$223.38	$223.40	$223.40
Purchase #6	$70.27	5.193%	$73.9191	$73.92	$73.90	$73.90
Purchase #7	$66.98	8.824%	$72.8903	$72.89	$72.90	$72.90
7 purchase totals =	$1,016.65		$1,104.5814	$1,104.58	$1,104.55	$1,104.70