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	$67.75	7.207%	$72.6327	$72.63	$72.65	$72.60
Purchase #2	$177.87	11.792%	$198.8444	$198.84	$198.85	$198.80
Purchase #3	$17.98	13.465%	$20.401	$20.40	$20.40	$20.40
Purchase #4	$162.92	7.374%	$174.9337	$174.93	$174.95	$174.90
Purchase #5	$127.90	8.808%	$139.1654	$139.17	$139.15	$139.20
Purchase #6	$57.38	6.538%	$61.1315	$61.13	$61.15	$61.10
Purchase #7	$47.45	6.149%	$50.3677	$50.37	$50.35	$50.40
7 purchase totals =	$659.25		$717.4764	$717.47	$717.50	$717.40