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	$198.73	5.850%	$210.3557	$210.36	$210.35	$210.40
Purchase #2	$91.81	4.339%	$95.7936	$95.79	$95.80	$95.80
Purchase #3	$206.83	10.645%	$228.8471	$228.85	$228.85	$228.80
Purchase #4	$99.46	11.831%	$111.2271	$111.23	$111.25	$111.20
Purchase #5	$16.98	10.686%	$18.7945	$18.79	$18.80	$18.80
Purchase #6	$58.69	6.602%	$62.5647	$62.56	$62.55	$62.60
Purchase #7	$233.61	3.240%	$241.179	$241.18	$241.20	$241.20
7 purchase totals =	$906.11		$968.7617	$968.76	$968.80	$968.80