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	$168.74	13.255%	$191.1065	$191.11	$191.10	$191.10
Purchase #2	$212.95	13.386%	$241.4555	$241.46	$241.45	$241.50
Purchase #3	$215.48	5.743%	$227.855	$227.86	$227.85	$227.90
Purchase #4	$226.40	13.859%	$257.7768	$257.78	$257.80	$257.80
Purchase #5	$110.98	8.812%	$120.7596	$120.76	$120.75	$120.80
Purchase #6	$78.49	5.865%	$83.0934	$83.09	$83.10	$83.10
Purchase #7	$108.31	3.285%	$111.868	$111.87	$111.85	$111.90
7 purchase totals =	$1,121.35		$1,233.9148	$1,233.93	$1,233.90	$1,234.10