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	$20.81	4.873%	$21.8241	$21.82	$21.80	$21.80
Purchase #2	$30.72	10.197%	$33.8525	$33.85	$33.85	$33.90
Purchase #3	$161.41	13.685%	$183.499	$183.50	$183.50	$183.50
Purchase #4	$243.27	7.834%	$262.3278	$262.33	$262.35	$262.30
Purchase #5	$108.65	4.123%	$113.1296	$113.13	$113.15	$113.10
Purchase #6	$150.99	13.798%	$171.8236	$171.82	$171.80	$171.80
Purchase #7	$167.57	12.211%	$188.032	$188.03	$188.05	$188.00
7 purchase totals =	$883.42		$974.4886	$974.48	$974.50	$974.40