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	$201.79	12.263%	$226.5355	$226.54	$226.55	$226.50
Purchase #2	$76.32	5.539%	$80.5474	$80.55	$80.55	$80.50
Purchase #3	$46.85	12.621%	$52.7629	$52.76	$52.75	$52.80
Purchase #4	$54.37	9.656%	$59.62	$59.62	$59.60	$59.60
Purchase #5	$102.91	7.401%	$110.5264	$110.53	$110.55	$110.50
Purchase #6	$229.34	11.436%	$255.5673	$255.57	$255.55	$255.60
Purchase #7	$212.95	4.381%	$222.2793	$222.28	$222.30	$222.30
7 purchase totals =	$924.53		$1,007.8388	$1,007.85	$1,007.85	$1,007.80