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	$168.25	10.528%	$185.9634	$185.96	$185.95	$186.00
Purchase #2	$173.32	12.618%	$195.1895	$195.19	$195.20	$195.20
Purchase #3	$160.96	6.290%	$171.0844	$171.08	$171.10	$171.10
Purchase #4	$78.30	8.577%	$85.0158	$85.02	$85.00	$85.00
Purchase #5	$126.34	8.142%	$136.6266	$136.63	$136.65	$136.60
Purchase #6	$100.43	6.854%	$107.3135	$107.31	$107.30	$107.30
Purchase #7	$199.40	9.872%	$219.0848	$219.08	$219.10	$219.10
7 purchase totals =	$1,007.00		$1,100.2780	$1,100.27	$1,100.30	$1,100.30