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	$42.75	13.571%	$48.5516	$48.55	$48.55	$48.60
Purchase #2	$110.48	4.522%	$115.4759	$115.48	$115.50	$115.50
Purchase #3	$77.94	5.184%	$81.9804	$81.98	$82.00	$82.00
Purchase #4	$65.84	8.845%	$71.6635	$71.66	$71.65	$71.70
Purchase #5	$11.63	9.693%	$12.7573	$12.76	$12.75	$12.80
Purchase #6	$164.44	4.485%	$171.8151	$171.82	$171.80	$171.80
Purchase #7	$133.26	11.113%	$148.0692	$148.07	$148.05	$148.10
7 purchase totals =	$606.34		$650.3130	$650.32	$650.30	$650.50