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	$119.70	3.191%	$123.5196	$123.52	$123.50	$123.50
Purchase #2	$61.78	4.308%	$64.4415	$64.44	$64.45	$64.40
Purchase #3	$172.80	4.330%	$180.2822	$180.28	$180.30	$180.30
Purchase #4	$5.60	7.711%	$6.0318	$6.03	$6.05	$6.00
Purchase #5	$168.77	13.319%	$191.2485	$191.25	$191.25	$191.20
Purchase #6	$111.61	4.331%	$116.4438	$116.44	$116.45	$116.40
Purchase #7	$77.73	6.541%	$82.8143	$82.81	$82.80	$82.80
7 purchase totals =	$717.99		$764.7817	$764.77	$764.80	$764.60