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	$47.48	11.428%	$52.906	$52.91	$52.90	$52.90
Purchase #2	$17.55	3.321%	$18.1328	$18.13	$18.15	$18.10
Purchase #3	$128.31	9.422%	$140.3994	$140.40	$140.40	$140.40
Purchase #4	$182.27	3.396%	$188.4599	$188.46	$188.45	$188.50
Purchase #5	$244.97	4.747%	$256.5987	$256.60	$256.60	$256.60
Purchase #6	$247.32	3.441%	$255.8303	$255.83	$255.85	$255.80
Purchase #7	$145.55	3.455%	$150.5788	$150.58	$150.60	$150.60
7 purchase totals =	$1,013.45		$1,062.9059	$1,062.91	$1,062.95	$1,062.90