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	$98.62	5.739%	$104.2798	$104.28	$104.30	$104.30
Purchase #2	$183.32	12.645%	$206.5008	$206.50	$206.50	$206.50
Purchase #3	$41.33	13.771%	$47.0216	$47.02	$47.00	$47.00
Purchase #4	$223.35	13.521%	$253.5492	$253.55	$253.55	$253.50
Purchase #5	$47.85	3.367%	$49.4611	$49.46	$49.45	$49.50
Purchase #6	$80.42	12.503%	$90.4749	$90.47	$90.45	$90.50
Purchase #7	$201.51	8.349%	$218.3341	$218.33	$218.35	$218.30
7 purchase totals =	$876.40		$969.6215	$969.61	$969.60	$969.60