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	$230.74	5.861%	$244.2637	$244.26	$244.25	$244.30
Purchase #2	$81.86	3.849%	$85.0108	$85.01	$85.00	$85.00
Purchase #3	$206.71	8.298%	$223.8628	$223.86	$223.85	$223.90
Purchase #4	$208.82	5.749%	$220.8251	$220.83	$220.85	$220.80
Purchase #5	$195.90	9.261%	$214.0423	$214.04	$214.05	$214.00
Purchase #6	$85.32	5.215%	$89.7694	$89.77	$89.75	$89.80
Purchase #7	$180.64	4.411%	$188.608	$188.61	$188.60	$188.60
7 purchase totals =	$1,189.99		$1,266.3821	$1,266.38	$1,266.35	$1,266.40