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	$78.89	3.447%	$81.6093	$81.61	$81.60	$81.60
Purchase #2	$92.55	12.326%	$103.9577	$103.96	$103.95	$104.00
Purchase #3	$130.84	13.403%	$148.3765	$148.38	$148.40	$148.40
Purchase #4	$130.33	3.171%	$134.4628	$134.46	$134.45	$134.50
Purchase #5	$248.51	4.839%	$260.5354	$260.54	$260.55	$260.50
Purchase #6	$166.53	4.805%	$174.5318	$174.53	$174.55	$174.50
Purchase #7	$151.28	13.145%	$171.1658	$171.17	$171.15	$171.20
7 purchase totals =	$998.93		$1,074.6393	$1,074.65	$1,074.65	$1,074.70