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	$249.40	5.586%	$263.3315	$263.33	$263.35	$263.30
Purchase #2	$83.67	4.332%	$87.2946	$87.29	$87.30	$87.30
Purchase #3	$209.96	7.155%	$224.9826	$224.98	$225.00	$225.00
Purchase #4	$83.42	5.603%	$88.094	$88.09	$88.10	$88.10
Purchase #5	$234.63	3.822%	$243.5976	$243.60	$243.60	$243.60
Purchase #6	$141.33	7.472%	$151.8902	$151.89	$151.90	$151.90
Purchase #7	$151.82	7.294%	$162.8938	$162.89	$162.90	$162.90
7 purchase totals =	$1,154.23		$1,222.0843	$1,222.07	$1,222.15	$1,222.10