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	$86.66	3.166%	$89.4037	$89.40	$89.40	$89.40
Purchase #2	$134.57	11.128%	$149.5449	$149.54	$149.55	$149.50
Purchase #3	$195.60	6.283%	$207.8895	$207.89	$207.90	$207.90
Purchase #4	$108.65	5.280%	$114.3867	$114.39	$114.40	$114.40
Purchase #5	$235.87	4.236%	$245.8615	$245.86	$245.85	$245.90
Purchase #6	$191.41	4.204%	$199.4569	$199.46	$199.45	$199.50
Purchase #7	$57.84	3.439%	$59.8291	$59.83	$59.85	$59.80
7 purchase totals =	$1,010.60		$1,066.3723	$1,066.37	$1,066.40	$1,066.40