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	$203.25	12.475%	$228.6054	$228.61	$228.60	$228.60
Purchase #2	$53.28	3.694%	$55.2482	$55.25	$55.25	$55.20
Purchase #3	$205.36	9.350%	$224.5612	$224.56	$224.55	$224.60
Purchase #4	$44.87	6.172%	$47.6394	$47.64	$47.65	$47.60
Purchase #5	$89.88	10.321%	$99.1565	$99.16	$99.15	$99.20
Purchase #6	$67.39	5.455%	$71.0661	$71.07	$71.05	$71.10
Purchase #7	$56.66	8.731%	$61.607	$61.61	$61.60	$61.60
7 purchase totals =	$720.69		$787.8838	$787.90	$787.85	$787.90