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	$95.50	9.756%	$104.817	$104.82	$104.80	$104.80
Purchase #2	$191.31	13.518%	$217.1713	$217.17	$217.15	$217.20
Purchase #3	$46.59	12.315%	$52.3276	$52.33	$52.35	$52.30
Purchase #4	$190.93	12.463%	$214.7256	$214.73	$214.75	$214.70
Purchase #5	$118.49	4.200%	$123.4666	$123.47	$123.45	$123.50
Purchase #6	$171.69	7.242%	$184.1238	$184.12	$184.10	$184.10
Purchase #7	$68.90	13.517%	$78.2132	$78.21	$78.20	$78.20
7 purchase totals =	$883.41		$974.8451	$974.85	$974.80	$974.80