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	$182.37	9.437%	$199.5803	$199.58	$199.60	$199.60
Purchase #2	$218.91	5.650%	$231.2784	$231.28	$231.30	$231.30
Purchase #3	$173.82	7.826%	$187.4232	$187.42	$187.40	$187.40
Purchase #4	$104.31	4.824%	$109.3419	$109.34	$109.35	$109.30
Purchase #5	$223.43	7.696%	$240.6252	$240.63	$240.65	$240.60
Purchase #6	$198.27	6.537%	$211.2309	$211.23	$211.25	$211.20
Purchase #7	$71.26	8.140%	$77.0606	$77.06	$77.05	$77.10
7 purchase totals =	$1,172.37		$1,256.5405	$1,256.54	$1,256.60	$1,256.50