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	$237.74	11.243%	$264.4691	$264.47	$264.45	$264.50
Purchase #2	$34.72	6.346%	$36.9233	$36.92	$36.90	$36.90
Purchase #3	$91.59	12.360%	$102.9105	$102.91	$102.90	$102.90
Purchase #4	$101.32	12.661%	$114.1481	$114.15	$114.15	$114.10
Purchase #5	$10.49	12.198%	$11.7696	$11.77	$11.75	$11.80
Purchase #6	$30.64	4.868%	$32.1316	$32.13	$32.15	$32.10
Purchase #7	$180.54	3.758%	$187.3247	$187.32	$187.30	$187.30
7 purchase totals =	$687.04		$749.6769	$749.67	$749.60	$749.60