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	$202.27	3.705%	$209.7641	$209.76	$209.75	$209.80
Purchase #2	$136.42	11.761%	$152.4644	$152.46	$152.45	$152.50
Purchase #3	$225.81	8.212%	$244.3535	$244.35	$244.35	$244.40
Purchase #4	$85.71	5.194%	$90.1618	$90.16	$90.15	$90.20
Purchase #5	$47.49	9.382%	$51.9455	$51.95	$51.95	$51.90
Purchase #6	$94.66	10.257%	$104.3693	$104.37	$104.35	$104.40
Purchase #7	$173.37	12.110%	$194.3651	$194.37	$194.35	$194.40
7 purchase totals =	$965.73		$1,047.4237	$1,047.42	$1,047.35	$1,047.60