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	$189.73	5.861%	$200.8501	$200.85	$200.85	$200.90
Purchase #2	$215.74	4.408%	$225.2498	$225.25	$225.25	$225.20
Purchase #3	$144.66	7.772%	$155.903	$155.90	$155.90	$155.90
Purchase #4	$43.90	12.396%	$49.3418	$49.34	$49.35	$49.30
Purchase #5	$54.46	9.364%	$59.5596	$59.56	$59.55	$59.60
Purchase #6	$160.86	10.552%	$177.8339	$177.83	$177.85	$177.80
Purchase #7	$206.28	13.800%	$234.7466	$234.75	$234.75	$234.70
7 purchase totals =	$1,015.63		$1,103.4848	$1,103.48	$1,103.50	$1,103.40