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	$98.86	8.844%	$107.6032	$107.60	$107.60	$107.60
Purchase #2	$119.85	5.609%	$126.5724	$126.57	$126.55	$126.60
Purchase #3	$150.77	13.723%	$171.4602	$171.46	$171.45	$171.50
Purchase #4	$128.97	11.758%	$144.1343	$144.13	$144.15	$144.10
Purchase #5	$212.53	4.698%	$222.5147	$222.51	$222.50	$222.50
Purchase #6	$90.74	6.845%	$96.9512	$96.95	$96.95	$97.00
Purchase #7	$133.59	10.346%	$147.4112	$147.41	$147.40	$147.40
7 purchase totals =	$935.31		$1,016.6472	$1,016.63	$1,016.60	$1,016.70