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	$42.32	13.179%	$47.8974	$47.90	$47.90	$47.90
Purchase #2	$134.84	13.718%	$153.3374	$153.34	$153.35	$153.30
Purchase #3	$84.39	6.765%	$90.099	$90.10	$90.10	$90.10
Purchase #4	$100.31	5.821%	$106.149	$106.15	$106.15	$106.10
Purchase #5	$208.77	12.175%	$234.1877	$234.19	$234.20	$234.20
Purchase #6	$145.70	9.872%	$160.0835	$160.08	$160.10	$160.10
Purchase #7	$79.73	7.716%	$85.882	$85.88	$85.90	$85.90
7 purchase totals =	$796.06		$877.6360	$877.64	$877.70	$877.60