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	$65.34	13.403%	$74.0975	$74.10	$74.10	$74.10
Purchase #2	$29.40	13.514%	$33.3731	$33.37	$33.35	$33.40
Purchase #3	$150.41	9.316%	$164.4222	$164.42	$164.40	$164.40
Purchase #4	$147.98	11.855%	$165.523	$165.52	$165.50	$165.50
Purchase #5	$222.58	10.336%	$245.5859	$245.59	$245.60	$245.60
Purchase #6	$113.87	8.770%	$123.8564	$123.86	$123.85	$123.90
Purchase #7	$128.95	10.451%	$142.4266	$142.43	$142.45	$142.40
7 purchase totals =	$858.53		$949.2847	$949.29	$949.25	$949.30