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	$39.65	4.475%	$41.4243	$41.42	$41.40	$41.40
Purchase #2	$6.86	4.274%	$7.1532	$7.15	$7.15	$7.20
Purchase #3	$240.69	12.143%	$269.917	$269.92	$269.90	$269.90
Purchase #4	$145.45	7.719%	$156.6773	$156.68	$156.70	$156.70
Purchase #5	$114.61	11.260%	$127.5151	$127.52	$127.50	$127.50
Purchase #6	$87.32	13.581%	$99.1789	$99.18	$99.20	$99.20
Purchase #7	$128.28	11.861%	$143.4953	$143.50	$143.50	$143.50
7 purchase totals =	$762.86		$845.3611	$845.37	$845.35	$845.40