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	$233.98	13.764%	$266.185	$266.19	$266.20	$266.20
Purchase #2	$166.88	5.540%	$176.1252	$176.13	$176.15	$176.10
Purchase #3	$47.71	3.500%	$49.3799	$49.38	$49.40	$49.40
Purchase #4	$79.83	11.836%	$89.2787	$89.28	$89.30	$89.30
Purchase #5	$179.72	3.770%	$186.4954	$186.50	$186.50	$186.50
Purchase #6	$149.35	11.452%	$166.4536	$166.45	$166.45	$166.50
Purchase #7	$131.73	8.186%	$142.5134	$142.51	$142.50	$142.50
7 purchase totals =	$989.20		$1,076.4312	$1,076.44	$1,076.50	$1,076.50