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	$103.92	3.740%	$107.8066	$107.81	$107.80	$107.80
Purchase #2	$108.45	13.696%	$123.3033	$123.30	$123.30	$123.30
Purchase #3	$208.88	11.222%	$232.3205	$232.32	$232.30	$232.30
Purchase #4	$108.30	4.580%	$113.2601	$113.26	$113.25	$113.30
Purchase #5	$133.90	13.432%	$151.8854	$151.89	$151.90	$151.90
Purchase #6	$116.39	3.598%	$120.5777	$120.58	$120.60	$120.60
Purchase #7	$213.75	7.290%	$229.3324	$229.33	$229.35	$229.30
7 purchase totals =	$993.59		$1,078.4860	$1,078.49	$1,078.50	$1,078.50