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	$234.46	5.196%	$246.6425	$246.64	$246.65	$246.60
Purchase #2	$31.29	6.758%	$33.4046	$33.40	$33.40	$33.40
Purchase #3	$145.94	11.325%	$162.4677	$162.47	$162.45	$162.50
Purchase #4	$205.85	7.164%	$220.5971	$220.60	$220.60	$220.60
Purchase #5	$168.65	13.439%	$191.3149	$191.31	$191.30	$191.30
Purchase #6	$240.86	12.555%	$271.1	$271.10	$271.10	$271.10
Purchase #7	$56.90	4.408%	$59.4082	$59.41	$59.40	$59.40
7 purchase totals =	$1,083.95		$1,184.9350	$1,184.93	$1,184.90	$1,184.90