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	$211.73	3.522%	$219.1871	$219.19	$219.20	$219.20
Purchase #2	$38.63	6.723%	$41.2271	$41.23	$41.25	$41.20
Purchase #3	$117.27	6.155%	$124.488	$124.49	$124.50	$124.50
Purchase #4	$190.43	4.459%	$198.9213	$198.92	$198.90	$198.90
Purchase #5	$238.90	4.555%	$249.7819	$249.78	$249.80	$249.80
Purchase #6	$88.27	12.708%	$99.4874	$99.49	$99.50	$99.50
Purchase #7	$215.45	6.602%	$229.674	$229.67	$229.65	$229.70
7 purchase totals =	$1,100.68		$1,162.7668	$1,162.77	$1,162.80	$1,162.80