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	$176.85	13.370%	$200.4948	$200.49	$200.50	$200.50
Purchase #2	$101.56	8.492%	$110.1845	$110.18	$110.20	$110.20
Purchase #3	$94.89	7.567%	$102.0703	$102.07	$102.05	$102.10
Purchase #4	$220.46	13.358%	$249.909	$249.91	$249.90	$249.90
Purchase #5	$178.59	8.134%	$193.1165	$193.12	$193.10	$193.10
Purchase #6	$150.53	11.688%	$168.1239	$168.12	$168.10	$168.10
Purchase #7	$98.71	5.443%	$104.0828	$104.08	$104.10	$104.10
7 purchase totals =	$1,021.59		$1,127.9818	$1,127.97	$1,127.95	$1,128.00