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	$54.49	9.340%	$59.5794	$59.58	$59.60	$59.60
Purchase #2	$200.44	12.742%	$225.9801	$225.98	$226.00	$226.00
Purchase #3	$216.69	9.791%	$237.9061	$237.91	$237.90	$237.90
Purchase #4	$5.31	5.421%	$5.5979	$5.60	$5.60	$5.60
Purchase #5	$52.28	5.492%	$55.1512	$55.15	$55.15	$55.20
Purchase #6	$83.40	5.680%	$88.1371	$88.14	$88.15	$88.10
Purchase #7	$96.36	13.630%	$109.4939	$109.49	$109.50	$109.50
7 purchase totals =	$708.97		$781.8457	$781.85	$781.90	$781.90