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	$227.76	6.810%	$243.2705	$243.27	$243.25	$243.30
Purchase #2	$245.55	10.158%	$270.493	$270.49	$270.50	$270.50
Purchase #3	$89.88	7.441%	$96.568	$96.57	$96.55	$96.60
Purchase #4	$65.53	9.429%	$71.7088	$71.71	$71.70	$71.70
Purchase #5	$248.87	7.808%	$268.3018	$268.30	$268.30	$268.30
Purchase #6	$85.52	10.232%	$94.2704	$94.27	$94.25	$94.30
Purchase #7	$24.31	4.262%	$25.3461	$25.35	$25.35	$25.30
7 purchase totals =	$987.42		$1,069.9586	$1,069.96	$1,069.90	$1,070.00