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	$48.44	5.445%	$51.0776	$51.08	$51.10	$51.10
Purchase #2	$7.36	5.565%	$7.7696	$7.77	$7.75	$7.80
Purchase #3	$78.44	12.847%	$88.5172	$88.52	$88.50	$88.50
Purchase #4	$73.41	6.870%	$78.4533	$78.45	$78.45	$78.50
Purchase #5	$141.85	9.491%	$155.313	$155.31	$155.30	$155.30
Purchase #6	$104.62	5.723%	$110.6074	$110.61	$110.60	$110.60
Purchase #7	$76.33	8.624%	$82.9127	$82.91	$82.90	$82.90
7 purchase totals =	$530.45		$574.6508	$574.65	$574.60	$574.70