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	$97.54	7.153%	$104.517	$104.52	$104.50	$104.50
Purchase #2	$55.27	7.269%	$59.2876	$59.29	$59.30	$59.30
Purchase #3	$74.92	10.350%	$82.6742	$82.67	$82.65	$82.70
Purchase #4	$211.46	7.549%	$227.4231	$227.42	$227.40	$227.40
Purchase #5	$175.52	6.804%	$187.4624	$187.46	$187.45	$187.50
Purchase #6	$114.29	6.746%	$122	$122.00	$122.00	$122.00
Purchase #7	$209.71	4.851%	$219.883	$219.88	$219.90	$219.90
7 purchase totals =	$938.71		$1,003.2473	$1,003.24	$1,003.20	$1,003.30