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	$87.93	3.166%	$90.7139	$90.71	$90.70	$90.70
Purchase #2	$175.73	11.680%	$196.2553	$196.26	$196.25	$196.30
Purchase #3	$212.41	4.127%	$221.1762	$221.18	$221.20	$221.20
Purchase #4	$211.55	3.730%	$219.4408	$219.44	$219.45	$219.40
Purchase #5	$134.37	7.496%	$144.4424	$144.44	$144.45	$144.40
Purchase #6	$120.36	6.279%	$127.9174	$127.92	$127.90	$127.90
Purchase #7	$59.37	6.287%	$63.1026	$63.10	$63.10	$63.10
7 purchase totals =	$1,001.72		$1,063.0486	$1,063.05	$1,063.05	$1,063.00