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	$33.56	13.786%	$38.1866	$38.19	$38.20	$38.20
Purchase #2	$176.38	11.472%	$196.6143	$196.61	$196.60	$196.60
Purchase #3	$198.50	10.701%	$219.7415	$219.74	$219.75	$219.70
Purchase #4	$182.51	3.293%	$188.5201	$188.52	$188.50	$188.50
Purchase #5	$139.48	7.227%	$149.5602	$149.56	$149.55	$149.60
Purchase #6	$232.73	12.347%	$261.4652	$261.47	$261.45	$261.50
Purchase #7	$149.32	8.700%	$162.3108	$162.31	$162.30	$162.30
7 purchase totals =	$1,112.48		$1,216.3987	$1,216.40	$1,216.35	$1,216.40