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	$61.32	6.873%	$65.5345	$65.53	$65.55	$65.50
Purchase #2	$32.31	9.276%	$35.3071	$35.31	$35.30	$35.30
Purchase #3	$109.87	6.159%	$116.6369	$116.64	$116.65	$116.60
Purchase #4	$154.84	6.801%	$165.3707	$165.37	$165.35	$165.40
Purchase #5	$243.59	12.257%	$273.4468	$273.45	$273.45	$273.40
Purchase #6	$194.99	10.572%	$215.6043	$215.60	$215.60	$215.60
Purchase #7	$66.91	5.245%	$70.4194	$70.42	$70.40	$70.40
7 purchase totals =	$863.83		$942.3197	$942.32	$942.30	$942.20