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	$217.71	5.543%	$229.7777	$229.78	$229.80	$229.80
Purchase #2	$59.88	11.708%	$66.8908	$66.89	$66.90	$66.90
Purchase #3	$123.26	13.394%	$139.7694	$139.77	$139.75	$139.80
Purchase #4	$213.42	7.231%	$228.8524	$228.85	$228.85	$228.90
Purchase #5	$95.47	9.326%	$104.3735	$104.37	$104.35	$104.40
Purchase #6	$232.61	6.423%	$247.5505	$247.55	$247.55	$247.60
Purchase #7	$82.82	5.125%	$87.0645	$87.06	$87.05	$87.10
7 purchase totals =	$1,025.17		$1,104.2788	$1,104.27	$1,104.25	$1,104.50