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	$212.40	9.845%	$233.3108	$233.31	$233.30	$233.30
Purchase #2	$218.97	4.401%	$228.6069	$228.61	$228.60	$228.60
Purchase #3	$161.33	12.474%	$181.4543	$181.45	$181.45	$181.50
Purchase #4	$162.26	7.629%	$174.6388	$174.64	$174.65	$174.60
Purchase #5	$101.78	11.203%	$113.1824	$113.18	$113.20	$113.20
Purchase #6	$189.33	3.690%	$196.3163	$196.32	$196.30	$196.30
Purchase #7	$222.45	3.164%	$229.4883	$229.49	$229.50	$229.50
7 purchase totals =	$1,268.52		$1,356.9978	$1,357.00	$1,357.00	$1,357.00