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	$167.73	10.641%	$185.5781	$185.58	$185.60	$185.60
Purchase #2	$84.78	9.356%	$92.712	$92.71	$92.70	$92.70
Purchase #3	$240.33	11.595%	$268.1963	$268.20	$268.20	$268.20
Purchase #4	$86.26	4.172%	$89.8588	$89.86	$89.85	$89.90
Purchase #5	$118.72	4.268%	$123.787	$123.79	$123.80	$123.80
Purchase #6	$166.86	10.127%	$183.7579	$183.76	$183.75	$183.80
Purchase #7	$20.33	4.228%	$21.1896	$21.19	$21.20	$21.20
7 purchase totals =	$885.01		$965.0797	$965.09	$965.10	$965.20