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	$213.51	9.704%	$234.229	$234.23	$234.25	$234.20
Purchase #2	$207.52	8.512%	$225.1841	$225.18	$225.20	$225.20
Purchase #3	$42.72	11.708%	$47.7217	$47.72	$47.70	$47.70
Purchase #4	$67.25	6.267%	$71.4646	$71.46	$71.45	$71.50
Purchase #5	$151.82	10.688%	$168.0465	$168.05	$168.05	$168.00
Purchase #6	$69.86	12.813%	$78.8112	$78.81	$78.80	$78.80
Purchase #7	$39.64	9.228%	$43.298	$43.30	$43.30	$43.30
7 purchase totals =	$792.32		$868.7551	$868.75	$868.75	$868.70