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	$110.95	3.582%	$114.9242	$114.92	$114.90	$114.90
Purchase #2	$116.62	13.320%	$132.1538	$132.15	$132.15	$132.20
Purchase #3	$99.71	5.747%	$105.4403	$105.44	$105.45	$105.40
Purchase #4	$83.40	8.458%	$90.454	$90.45	$90.45	$90.50
Purchase #5	$225.55	13.359%	$255.6812	$255.68	$255.70	$255.70
Purchase #6	$41.32	4.314%	$43.1025	$43.10	$43.10	$43.10
Purchase #7	$88.89	8.717%	$96.6385	$96.64	$96.65	$96.60
7 purchase totals =	$766.44		$838.3945	$838.38	$838.40	$838.40