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	$52.32	13.277%	$59.2665	$59.27	$59.25	$59.30
Purchase #2	$77.29	11.517%	$86.1915	$86.19	$86.20	$86.20
Purchase #3	$16.41	11.695%	$18.3291	$18.33	$18.35	$18.30
Purchase #4	$227.54	13.808%	$258.9587	$258.96	$258.95	$259.00
Purchase #5	$128.27	13.436%	$145.5044	$145.50	$145.50	$145.50
Purchase #6	$216.31	11.385%	$240.9369	$240.94	$240.95	$240.90
Purchase #7	$184.98	7.151%	$198.2079	$198.21	$198.20	$198.20
7 purchase totals =	$903.12		$1,007.3950	$1,007.40	$1,007.40	$1,007.40