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	$59.53	8.529%	$64.6073	$64.61	$64.60	$64.60
Purchase #2	$70.34	8.801%	$76.5306	$76.53	$76.55	$76.50
Purchase #3	$85.77	12.861%	$96.8009	$96.80	$96.80	$96.80
Purchase #4	$243.30	5.346%	$256.3068	$256.31	$256.30	$256.30
Purchase #5	$109.65	13.577%	$124.5372	$124.54	$124.55	$124.50
Purchase #6	$242.32	10.406%	$267.5358	$267.54	$267.55	$267.50
Purchase #7	$190.92	11.770%	$213.3913	$213.39	$213.40	$213.40
7 purchase totals =	$1,001.83		$1,099.7099	$1,099.72	$1,099.75	$1,099.60