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	$167.46	3.849%	$173.9055	$173.91	$173.90	$173.90
Purchase #2	$170.81	7.706%	$183.9726	$183.97	$183.95	$184.00
Purchase #3	$141.39	10.504%	$156.2416	$156.24	$156.25	$156.20
Purchase #4	$153.98	6.647%	$164.2151	$164.22	$164.20	$164.20
Purchase #5	$81.72	9.333%	$89.3469	$89.35	$89.35	$89.30
Purchase #6	$94.41	13.788%	$107.4273	$107.43	$107.45	$107.40
Purchase #7	$97.77	3.842%	$101.5263	$101.53	$101.55	$101.50
7 purchase totals =	$907.54		$976.6353	$976.65	$976.65	$976.50