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	$125.34	8.451%	$135.9325	$135.93	$135.95	$135.90
Purchase #2	$113.60	12.624%	$127.9409	$127.94	$127.95	$127.90
Purchase #3	$107.59	11.794%	$120.2792	$120.28	$120.30	$120.30
Purchase #4	$28.52	3.442%	$29.5017	$29.50	$29.50	$29.50
Purchase #5	$95.73	7.653%	$103.0562	$103.06	$103.05	$103.10
Purchase #6	$12.54	13.826%	$14.2738	$14.27	$14.25	$14.30
Purchase #7	$183.46	7.107%	$196.4985	$196.50	$196.50	$196.50
7 purchase totals =	$666.78		$727.4828	$727.48	$727.50	$727.50