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	$44.33	13.775%	$50.4365	$50.44	$50.45	$50.40
Purchase #2	$103.94	3.466%	$107.5426	$107.54	$107.55	$107.50
Purchase #3	$78.69	9.155%	$85.8941	$85.89	$85.90	$85.90
Purchase #4	$185.79	6.773%	$198.3736	$198.37	$198.35	$198.40
Purchase #5	$174.39	9.479%	$190.9204	$190.92	$190.90	$190.90
Purchase #6	$177.76	7.852%	$191.7177	$191.72	$191.70	$191.70
Purchase #7	$20.90	8.205%	$22.6148	$22.61	$22.60	$22.60
7 purchase totals =	$785.80		$847.4997	$847.49	$847.45	$847.40