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	$187.74	4.769%	$196.6933	$196.69	$196.70	$196.70
Purchase #2	$74.74	11.763%	$83.5317	$83.53	$83.55	$83.50
Purchase #3	$71.35	12.173%	$80.0354	$80.04	$80.05	$80.00
Purchase #4	$237.51	13.634%	$269.8921	$269.89	$269.90	$269.90
Purchase #5	$127.31	7.845%	$137.2975	$137.30	$137.30	$137.30
Purchase #6	$128.78	5.704%	$136.1256	$136.13	$136.15	$136.10
Purchase #7	$32.78	3.464%	$33.9155	$33.92	$33.90	$33.90
7 purchase totals =	$860.21		$937.4911	$937.50	$937.55	$937.40