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	$79.30	12.796%	$89.4472	$89.45	$89.45	$89.40
Purchase #2	$35.56	4.190%	$37.05	$37.05	$37.05	$37.10
Purchase #3	$37.52	5.206%	$39.4733	$39.47	$39.45	$39.50
Purchase #4	$92.84	3.418%	$96.0133	$96.01	$96.00	$96.00
Purchase #5	$147.81	10.359%	$163.1216	$163.12	$163.10	$163.10
Purchase #6	$31.88	5.505%	$33.635	$33.64	$33.65	$33.60
Purchase #7	$224.83	7.441%	$241.5596	$241.56	$241.55	$241.60
7 purchase totals =	$649.74		$700.3000	$700.30	$700.25	$700.30