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	$249.79	11.145%	$277.6291	$277.63	$277.65	$277.60
Purchase #2	$230.62	10.524%	$254.8904	$254.89	$254.90	$254.90
Purchase #3	$210.36	9.561%	$230.4725	$230.47	$230.45	$230.50
Purchase #4	$83.96	13.175%	$95.0217	$95.02	$95.00	$95.00
Purchase #5	$113.54	8.732%	$123.4543	$123.45	$123.45	$123.50
Purchase #6	$224.38	11.497%	$250.177	$250.18	$250.20	$250.20
Purchase #7	$202.33	10.296%	$223.1619	$223.16	$223.15	$223.20
7 purchase totals =	$1,314.98		$1,454.8069	$1,454.80	$1,454.80	$1,454.90