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	$174.79	10.467%	$193.0853	$193.09	$193.10	$193.10
Purchase #2	$48.76	12.729%	$54.9667	$54.97	$54.95	$55.00
Purchase #3	$103.82	7.352%	$111.4528	$111.45	$111.45	$111.50
Purchase #4	$125.67	12.740%	$141.6804	$141.68	$141.70	$141.70
Purchase #5	$80.44	3.382%	$83.1605	$83.16	$83.15	$83.20
Purchase #6	$86.54	10.842%	$95.9227	$95.92	$95.90	$95.90
Purchase #7	$232.89	8.788%	$253.3564	$253.36	$253.35	$253.40
7 purchase totals =	$852.91		$933.6248	$933.63	$933.60	$933.80