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	$176.41	11.157%	$196.0921	$196.09	$196.10	$196.10
Purchase #2	$62.27	5.386%	$65.6239	$65.62	$65.60	$65.60
Purchase #3	$30.92	8.783%	$33.6357	$33.64	$33.65	$33.60
Purchase #4	$160.64	3.359%	$166.0359	$166.04	$166.05	$166.00
Purchase #5	$164.62	12.118%	$184.5687	$184.57	$184.55	$184.60
Purchase #6	$16.58	10.495%	$18.3201	$18.32	$18.30	$18.30
Purchase #7	$152.39	13.678%	$173.2339	$173.23	$173.25	$173.20
7 purchase totals =	$763.83		$837.5103	$837.51	$837.50	$837.40