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	$114.59	6.248%	$121.7496	$121.75	$121.75	$121.70
Purchase #2	$18.32	10.835%	$20.305	$20.31	$20.30	$20.30
Purchase #3	$139.47	4.380%	$145.5788	$145.58	$145.60	$145.60
Purchase #4	$242.56	13.187%	$274.5464	$274.55	$274.55	$274.50
Purchase #5	$249.85	5.843%	$264.4487	$264.45	$264.45	$264.40
Purchase #6	$207.44	10.646%	$229.5241	$229.52	$229.50	$229.50
Purchase #7	$167.78	10.328%	$185.1083	$185.11	$185.10	$185.10
7 purchase totals =	$1,140.01		$1,241.2609	$1,241.27	$1,241.25	$1,241.10