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	$204.30	3.345%	$211.1338	$211.13	$211.15	$211.10
Purchase #2	$134.31	6.181%	$142.6117	$142.61	$142.60	$142.60
Purchase #3	$165.25	9.430%	$180.8331	$180.83	$180.85	$180.80
Purchase #4	$167.94	12.440%	$188.8317	$188.83	$188.85	$188.80
Purchase #5	$238.58	10.102%	$262.6814	$262.68	$262.70	$262.70
Purchase #6	$232.64	7.275%	$249.5646	$249.56	$249.55	$249.60
Purchase #7	$158.31	8.217%	$171.3183	$171.32	$171.30	$171.30
7 purchase totals =	$1,301.33		$1,406.9746	$1,406.96	$1,407.00	$1,406.90