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	$139.92	9.286%	$152.913	$152.91	$152.90	$152.90
Purchase #2	$161.97	7.157%	$173.5622	$173.56	$173.55	$173.60
Purchase #3	$180.34	8.444%	$195.5679	$195.57	$195.55	$195.60
Purchase #4	$176.82	4.525%	$184.8211	$184.82	$184.80	$184.80
Purchase #5	$63.57	12.274%	$71.3726	$71.37	$71.35	$71.40
Purchase #6	$187.80	6.661%	$200.3094	$200.31	$200.30	$200.30
Purchase #7	$98.46	9.528%	$107.8413	$107.84	$107.85	$107.80
7 purchase totals =	$1,008.88		$1,086.3875	$1,086.38	$1,086.30	$1,086.40