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	$89.98	12.671%	$101.3814	$101.38	$101.40	$101.40
Purchase #2	$19.26	13.465%	$21.8534	$21.85	$21.85	$21.90
Purchase #3	$143.62	13.170%	$162.5348	$162.53	$162.55	$162.50
Purchase #4	$78.59	9.709%	$86.2203	$86.22	$86.20	$86.20
Purchase #5	$158.65	12.675%	$178.7589	$178.76	$178.75	$178.80
Purchase #6	$126.61	13.454%	$143.6441	$143.64	$143.65	$143.60
Purchase #7	$228.83	7.354%	$245.6582	$245.66	$245.65	$245.70
7 purchase totals =	$845.54		$940.0511	$940.04	$940.05	$940.10