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	$88.48	10.324%	$97.6147	$97.61	$97.60	$97.60
Purchase #2	$148.45	6.751%	$158.4719	$158.47	$158.45	$158.50
Purchase #3	$147.38	11.827%	$164.8106	$164.81	$164.80	$164.80
Purchase #4	$242.58	12.758%	$273.5284	$273.53	$273.55	$273.50
Purchase #5	$79.58	12.780%	$89.7503	$89.75	$89.75	$89.80
Purchase #6	$77.85	4.735%	$81.5362	$81.54	$81.55	$81.50
Purchase #7	$97.41	3.107%	$100.4365	$100.44	$100.45	$100.40
7 purchase totals =	$881.73		$966.1486	$966.15	$966.15	$966.10