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	$135.95	9.373%	$148.6926	$148.69	$148.70	$148.70
Purchase #2	$160.94	12.146%	$180.4878	$180.49	$180.50	$180.50
Purchase #3	$96.65	13.585%	$109.7799	$109.78	$109.80	$109.80
Purchase #4	$123.58	8.508%	$134.0942	$134.09	$134.10	$134.10
Purchase #5	$119.51	7.263%	$128.19	$128.19	$128.20	$128.20
Purchase #6	$38.72	10.739%	$42.8781	$42.88	$42.90	$42.90
Purchase #7	$241.52	10.250%	$266.2758	$266.28	$266.30	$266.30
7 purchase totals =	$916.87		$1,010.3984	$1,010.40	$1,010.50	$1,010.50