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	$167.51	10.767%	$185.5458	$185.55	$185.55	$185.50
Purchase #2	$39.74	10.416%	$43.8793	$43.88	$43.90	$43.90
Purchase #3	$101.60	9.204%	$110.9513	$110.95	$110.95	$111.00
Purchase #4	$55.47	11.207%	$61.6865	$61.69	$61.70	$61.70
Purchase #5	$105.52	13.339%	$119.5953	$119.60	$119.60	$119.60
Purchase #6	$221.44	10.711%	$245.1584	$245.16	$245.15	$245.20
Purchase #7	$141.52	6.773%	$151.1051	$151.11	$151.10	$151.10
7 purchase totals =	$832.80		$917.9217	$917.94	$917.95	$918.00