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	$229.85	4.420%	$240.0094	$240.01	$240.00	$240.00
Purchase #2	$235.94	7.790%	$254.3197	$254.32	$254.30	$254.30
Purchase #3	$86.85	13.188%	$98.3038	$98.30	$98.30	$98.30
Purchase #4	$217.44	9.711%	$238.5556	$238.56	$238.55	$238.60
Purchase #5	$73.58	3.709%	$76.3091	$76.31	$76.30	$76.30
Purchase #6	$91.47	9.619%	$100.2685	$100.27	$100.25	$100.30
Purchase #7	$82.31	7.683%	$88.6339	$88.63	$88.65	$88.60
7 purchase totals =	$1,017.44		$1,096.4000	$1,096.40	$1,096.35	$1,096.40