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	$130.27	5.682%	$137.6719	$137.67	$137.65	$137.70
Purchase #2	$87.67	4.272%	$91.4153	$91.42	$91.40	$91.40
Purchase #3	$41.88	12.524%	$47.1251	$47.13	$47.15	$47.10
Purchase #4	$41.52	4.373%	$43.3357	$43.34	$43.35	$43.30
Purchase #5	$244.83	10.244%	$269.9104	$269.91	$269.90	$269.90
Purchase #6	$88.38	3.403%	$91.3876	$91.39	$91.40	$91.40
Purchase #7	$249.78	13.770%	$284.1747	$284.17	$284.15	$284.20
7 purchase totals =	$884.33		$965.0207	$965.03	$965.00	$965.00