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	$32.39	10.403%	$35.7595	$35.76	$35.75	$35.80
Purchase #2	$13.83	3.606%	$14.3287	$14.33	$14.35	$14.30
Purchase #3	$166.26	3.323%	$171.7848	$171.78	$171.80	$171.80
Purchase #4	$47.63	10.491%	$52.6269	$52.63	$52.65	$52.60
Purchase #5	$176.63	12.251%	$198.2689	$198.27	$198.25	$198.30
Purchase #6	$250.39	11.348%	$278.8043	$278.80	$278.80	$278.80
Purchase #7	$82.76	3.780%	$85.8883	$85.89	$85.90	$85.90
7 purchase totals =	$769.89		$837.4614	$837.46	$837.50	$837.50