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	$213.55	10.473%	$235.9151	$235.92	$235.90	$235.90
Purchase #2	$174.65	4.822%	$183.0716	$183.07	$183.05	$183.10
Purchase #3	$98.53	13.616%	$111.9458	$111.95	$111.95	$111.90
Purchase #4	$182.92	7.479%	$196.6006	$196.60	$196.60	$196.60
Purchase #5	$64.36	10.533%	$71.139	$71.14	$71.15	$71.10
Purchase #6	$89.77	4.111%	$93.4604	$93.46	$93.45	$93.50
Purchase #7	$13.52	7.227%	$14.4971	$14.50	$14.50	$14.50
7 purchase totals =	$837.30		$906.6296	$906.64	$906.60	$906.60