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	$52.47	3.345%	$54.2251	$54.23	$54.25	$54.20
Purchase #2	$180.94	8.363%	$196.072	$196.07	$196.05	$196.10
Purchase #3	$121.90	9.122%	$133.0197	$133.02	$133.00	$133.00
Purchase #4	$105.42	5.721%	$111.4511	$111.45	$111.45	$111.50
Purchase #5	$99.67	3.722%	$103.3797	$103.38	$103.40	$103.40
Purchase #6	$61.62	5.645%	$65.0984	$65.10	$65.10	$65.10
Purchase #7	$242.91	9.180%	$265.2091	$265.21	$265.20	$265.20
7 purchase totals =	$864.93		$928.4551	$928.46	$928.45	$928.50