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	$104.75	13.411%	$118.798	$118.80	$118.80	$118.80
Purchase #2	$87.64	9.563%	$96.021	$96.02	$96.00	$96.00
Purchase #3	$83.69	6.627%	$89.2361	$89.24	$89.25	$89.20
Purchase #4	$196.80	6.609%	$209.8065	$209.81	$209.80	$209.80
Purchase #5	$28.72	3.800%	$29.8114	$29.81	$29.80	$29.80
Purchase #6	$50.80	10.240%	$56.0019	$56.00	$56.00	$56.00
Purchase #7	$178.35	5.488%	$188.1378	$188.14	$188.15	$188.10
7 purchase totals =	$730.75		$787.8127	$787.82	$787.80	$787.70