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	$238.87	10.774%	$264.6059	$264.61	$264.60	$264.60
Purchase #2	$59.94	8.791%	$65.2093	$65.21	$65.20	$65.20
Purchase #3	$178.34	11.547%	$198.9329	$198.93	$198.95	$198.90
Purchase #4	$94.57	6.524%	$100.7397	$100.74	$100.75	$100.70
Purchase #5	$109.86	9.542%	$120.3428	$120.34	$120.35	$120.30
Purchase #6	$63.93	10.434%	$70.6005	$70.60	$70.60	$70.60
Purchase #7	$242.65	13.710%	$275.9173	$275.92	$275.90	$275.90
7 purchase totals =	$988.16		$1,096.3484	$1,096.35	$1,096.35	$1,096.20