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	$217.76	9.654%	$238.7826	$238.78	$238.80	$238.80
Purchase #2	$150.30	12.336%	$168.841	$168.84	$168.85	$168.80
Purchase #3	$30.34	5.657%	$32.0563	$32.06	$32.05	$32.10
Purchase #4	$183.66	3.874%	$190.775	$190.78	$190.80	$190.80
Purchase #5	$113.52	12.143%	$127.3047	$127.30	$127.30	$127.30
Purchase #6	$198.51	9.851%	$218.0652	$218.07	$218.05	$218.10
Purchase #7	$125.55	3.350%	$129.7559	$129.76	$129.75	$129.80
7 purchase totals =	$1,019.64		$1,105.5807	$1,105.59	$1,105.60	$1,105.70