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	$150.48	8.229%	$162.863	$162.86	$162.85	$162.90
Purchase #2	$175.33	6.185%	$186.1742	$186.17	$186.15	$186.20
Purchase #3	$192.78	4.206%	$200.8883	$200.89	$200.90	$200.90
Purchase #4	$135.47	12.117%	$151.8849	$151.88	$151.90	$151.90
Purchase #5	$149.98	3.277%	$154.8948	$154.89	$154.90	$154.90
Purchase #6	$17.29	7.825%	$18.6429	$18.64	$18.65	$18.60
Purchase #7	$90.27	4.329%	$94.1778	$94.18	$94.20	$94.20
7 purchase totals =	$911.60		$969.5259	$969.51	$969.55	$969.60