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	$62.74	9.354%	$68.6087	$68.61	$68.60	$68.60
Purchase #2	$234.46	11.243%	$260.8203	$260.82	$260.80	$260.80
Purchase #3	$99.76	11.370%	$111.1027	$111.10	$111.10	$111.10
Purchase #4	$230.95	6.767%	$246.5784	$246.58	$246.60	$246.60
Purchase #5	$144.76	11.613%	$161.571	$161.57	$161.55	$161.60
Purchase #6	$98.60	12.818%	$111.2385	$111.24	$111.25	$111.20
Purchase #7	$64.37	5.203%	$67.7192	$67.72	$67.70	$67.70
7 purchase totals =	$935.64		$1,027.6388	$1,027.64	$1,027.60	$1,027.60