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	$61.49	3.355%	$63.553	$63.55	$63.55	$63.60
Purchase #2	$37.71	9.702%	$41.3686	$41.37	$41.35	$41.40
Purchase #3	$233.32	10.711%	$258.3109	$258.31	$258.30	$258.30
Purchase #4	$40.39	4.790%	$42.3247	$42.32	$42.30	$42.30
Purchase #5	$39.91	6.873%	$42.653	$42.65	$42.65	$42.70
Purchase #6	$230.34	7.727%	$248.1384	$248.14	$248.15	$248.10
Purchase #7	$34.69	8.693%	$37.7056	$37.71	$37.70	$37.70
7 purchase totals =	$677.85		$734.0542	$734.05	$734.00	$734.10