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	$179.79	4.235%	$187.4041	$187.40	$187.40	$187.40
Purchase #2	$176.34	7.378%	$189.3504	$189.35	$189.35	$189.40
Purchase #3	$183.38	3.579%	$189.9432	$189.94	$189.95	$189.90
Purchase #4	$237.64	6.831%	$253.8732	$253.87	$253.85	$253.90
Purchase #5	$102.74	6.417%	$109.3328	$109.33	$109.35	$109.30
Purchase #6	$174.49	4.655%	$182.6125	$182.61	$182.60	$182.60
Purchase #7	$51.81	4.409%	$54.0943	$54.09	$54.10	$54.10
7 purchase totals =	$1,106.19		$1,166.6105	$1,166.59	$1,166.60	$1,166.60