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	$134.49	11.570%	$150.0505	$150.05	$150.05	$150.10
Purchase #2	$86.34	6.285%	$91.7665	$91.77	$91.75	$91.80
Purchase #3	$157.60	13.264%	$178.5041	$178.50	$178.50	$178.50
Purchase #4	$70.40	13.482%	$79.8913	$79.89	$79.90	$79.90
Purchase #5	$90.81	7.224%	$97.3701	$97.37	$97.35	$97.40
Purchase #6	$62.49	3.779%	$64.8515	$64.85	$64.85	$64.90
Purchase #7	$89.42	11.799%	$99.9707	$99.97	$99.95	$100.00
7 purchase totals =	$691.55		$762.4047	$762.40	$762.35	$762.60