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	$190.60	5.348%	$200.7933	$200.79	$200.80	$200.80
Purchase #2	$147.51	11.380%	$164.2966	$164.30	$164.30	$164.30
Purchase #3	$67.42	7.675%	$72.5945	$72.59	$72.60	$72.60
Purchase #4	$230.57	4.869%	$241.7965	$241.80	$241.80	$241.80
Purchase #5	$168.73	7.278%	$181.0102	$181.01	$181.00	$181.00
Purchase #6	$225.71	8.374%	$244.611	$244.61	$244.60	$244.60
Purchase #7	$35.68	8.735%	$38.7966	$38.80	$38.80	$38.80
7 purchase totals =	$1,066.22		$1,143.8987	$1,143.90	$1,143.90	$1,143.90