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	$88.62	10.398%	$97.8347	$97.83	$97.85	$97.80
Purchase #2	$103.81	7.226%	$111.3113	$111.31	$111.30	$111.30
Purchase #3	$41.85	4.573%	$43.7638	$43.76	$43.75	$43.80
Purchase #4	$204.29	12.572%	$229.9733	$229.97	$229.95	$230.00
Purchase #5	$6.83	4.692%	$7.1505	$7.15	$7.15	$7.20
Purchase #6	$186.63	7.240%	$200.142	$200.14	$200.15	$200.10
Purchase #7	$168.83	10.768%	$187.0096	$187.01	$187.00	$187.00
7 purchase totals =	$800.86		$877.1852	$877.17	$877.15	$877.20