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	$138.96	6.683%	$148.2467	$148.25	$148.25	$148.20
Purchase #2	$181.62	5.607%	$191.8034	$191.80	$191.80	$191.80
Purchase #3	$185.27	5.789%	$195.9953	$196.00	$196.00	$196.00
Purchase #4	$168.60	11.264%	$187.5911	$187.59	$187.60	$187.60
Purchase #5	$78.26	6.233%	$83.1379	$83.14	$83.15	$83.10
Purchase #6	$176.51	3.361%	$182.4425	$182.44	$182.45	$182.40
Purchase #7	$173.45	13.307%	$196.531	$196.53	$196.55	$196.50
7 purchase totals =	$1,102.67		$1,185.7479	$1,185.75	$1,185.80	$1,185.60