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	$113.64	10.410%	$125.4699	$125.47	$125.45	$125.50
Purchase #2	$142.42	9.742%	$156.2946	$156.29	$156.30	$156.30
Purchase #3	$31.84	4.422%	$33.248	$33.25	$33.25	$33.20
Purchase #4	$30.54	10.546%	$33.7607	$33.76	$33.75	$33.80
Purchase #5	$77.92	6.131%	$82.6973	$82.70	$82.70	$82.70
Purchase #6	$104.49	6.472%	$111.2526	$111.25	$111.25	$111.30
Purchase #7	$96.57	4.168%	$100.595	$100.60	$100.60	$100.60
7 purchase totals =	$597.42		$643.3181	$643.32	$643.30	$643.40