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	$71.51	7.161%	$76.6308	$76.63	$76.65	$76.60
Purchase #2	$134.32	4.431%	$140.2717	$140.27	$140.25	$140.30
Purchase #3	$71.62	11.632%	$79.9508	$79.95	$79.95	$80.00
Purchase #4	$213.55	11.867%	$238.892	$238.89	$238.90	$238.90
Purchase #5	$141.59	7.821%	$152.6638	$152.66	$152.65	$152.70
Purchase #6	$133.96	6.386%	$142.5147	$142.51	$142.50	$142.50
Purchase #7	$166.39	11.715%	$185.8826	$185.88	$185.90	$185.90
7 purchase totals =	$932.94		$1,016.8064	$1,016.79	$1,016.80	$1,016.90