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	$105.29	11.429%	$117.3236	$117.32	$117.30	$117.30
Purchase #2	$69.40	4.113%	$72.2544	$72.25	$72.25	$72.30
Purchase #3	$136.83	9.560%	$149.9109	$149.91	$149.90	$149.90
Purchase #4	$60.57	10.758%	$67.0861	$67.09	$67.10	$67.10
Purchase #5	$119.84	6.443%	$127.5613	$127.56	$127.55	$127.60
Purchase #6	$71.72	4.675%	$75.0729	$75.07	$75.05	$75.10
Purchase #7	$135.70	10.241%	$149.597	$149.60	$149.60	$149.60
7 purchase totals =	$699.35		$758.8062	$758.80	$758.75	$758.90