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	$227.71	10.617%	$251.886	$251.89	$251.90	$251.90
Purchase #2	$49.84	5.450%	$52.5563	$52.56	$52.55	$52.60
Purchase #3	$32.60	10.203%	$35.9262	$35.93	$35.95	$35.90
Purchase #4	$101.38	8.416%	$109.9121	$109.91	$109.90	$109.90
Purchase #5	$56.68	9.813%	$62.242	$62.24	$62.25	$62.20
Purchase #6	$109.91	13.241%	$124.4632	$124.46	$124.45	$124.50
Purchase #7	$144.39	12.779%	$162.8416	$162.84	$162.85	$162.80
7 purchase totals =	$722.51		$799.8274	$799.83	$799.85	$799.80