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	$233.32	3.765%	$242.1045	$242.10	$242.10	$242.10
Purchase #2	$13.38	8.513%	$14.519	$14.52	$14.50	$14.50
Purchase #3	$76.69	9.481%	$83.961	$83.96	$83.95	$84.00
Purchase #4	$38.31	4.788%	$40.1443	$40.14	$40.15	$40.10
Purchase #5	$160.31	9.715%	$175.8841	$175.88	$175.90	$175.90
Purchase #6	$140.33	8.570%	$152.3563	$152.36	$152.35	$152.40
Purchase #7	$96.34	9.346%	$105.3439	$105.34	$105.35	$105.30
7 purchase totals =	$758.68		$814.3131	$814.30	$814.30	$814.30