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	$60.41	13.370%	$68.4868	$68.49	$68.50	$68.50
Purchase #2	$88.63	5.207%	$93.245	$93.25	$93.25	$93.20
Purchase #3	$103.67	8.131%	$112.0994	$112.10	$112.10	$112.10
Purchase #4	$35.50	5.311%	$37.3854	$37.39	$37.40	$37.40
Purchase #5	$134.59	13.725%	$153.0625	$153.06	$153.05	$153.10
Purchase #6	$93.77	6.819%	$100.1642	$100.16	$100.15	$100.20
Purchase #7	$208.50	7.383%	$223.8936	$223.89	$223.90	$223.90
7 purchase totals =	$725.07		$788.3369	$788.34	$788.35	$788.40