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	$242.81	5.727%	$256.7157	$256.72	$256.70	$256.70
Purchase #2	$177.59	3.521%	$183.8429	$183.84	$183.85	$183.80
Purchase #3	$103.43	7.383%	$111.0662	$111.07	$111.05	$111.10
Purchase #4	$98.54	4.711%	$103.1822	$103.18	$103.20	$103.20
Purchase #5	$148.60	12.628%	$167.3652	$167.37	$167.35	$167.40
Purchase #6	$93.59	13.276%	$106.015	$106.02	$106.00	$106.00
Purchase #7	$80.27	6.144%	$85.2018	$85.20	$85.20	$85.20
7 purchase totals =	$944.83		$1,013.3890	$1,013.40	$1,013.35	$1,013.40