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	$140.30	3.656%	$145.4294	$145.43	$145.45	$145.40
Purchase #2	$237.61	10.428%	$262.388	$262.39	$262.40	$262.40
Purchase #3	$223.27	6.788%	$238.4256	$238.43	$238.45	$238.40
Purchase #4	$64.66	6.481%	$68.8506	$68.85	$68.85	$68.90
Purchase #5	$43.44	7.604%	$46.7432	$46.74	$46.75	$46.70
Purchase #6	$38.99	7.753%	$42.0129	$42.01	$42.00	$42.00
Purchase #7	$151.27	8.774%	$164.5424	$164.54	$164.55	$164.50
7 purchase totals =	$899.54		$968.3921	$968.39	$968.45	$968.30