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	$129.98	13.745%	$147.8458	$147.85	$147.85	$147.80
Purchase #2	$114.54	3.565%	$118.6234	$118.62	$118.60	$118.60
Purchase #3	$79.91	12.813%	$90.1489	$90.15	$90.15	$90.10
Purchase #4	$83.91	7.270%	$90.0103	$90.01	$90.00	$90.00
Purchase #5	$44.41	6.539%	$47.314	$47.31	$47.30	$47.30
Purchase #6	$61.81	8.849%	$67.2796	$67.28	$67.30	$67.30
Purchase #7	$164.82	3.222%	$170.1305	$170.13	$170.15	$170.10
7 purchase totals =	$679.38		$731.3525	$731.35	$731.35	$731.20