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	$91.33	5.829%	$96.6536	$96.65	$96.65	$96.70
Purchase #2	$112.88	3.441%	$116.7642	$116.76	$116.75	$116.80
Purchase #3	$236.28	10.806%	$261.8124	$261.81	$261.80	$261.80
Purchase #4	$189.43	3.841%	$196.706	$196.71	$196.70	$196.70
Purchase #5	$121.86	9.267%	$133.1528	$133.15	$133.15	$133.20
Purchase #6	$224.39	13.353%	$254.3528	$254.35	$254.35	$254.40
Purchase #7	$101.39	10.717%	$112.256	$112.26	$112.25	$112.30
7 purchase totals =	$1,077.56		$1,171.6978	$1,171.69	$1,171.65	$1,171.90