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	$48.25	8.703%	$52.4492	$52.45	$52.45	$52.40
Purchase #2	$79.30	7.604%	$85.33	$85.33	$85.35	$85.30
Purchase #3	$150.39	4.126%	$156.5951	$156.60	$156.60	$156.60
Purchase #4	$77.47	10.296%	$85.4463	$85.45	$85.45	$85.40
Purchase #5	$34.27	12.428%	$38.5291	$38.53	$38.55	$38.50
Purchase #6	$173.55	9.201%	$189.5183	$189.52	$189.50	$189.50
Purchase #7	$93.78	6.157%	$99.554	$99.55	$99.55	$99.60
7 purchase totals =	$657.01		$707.4220	$707.43	$707.45	$707.30