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	$73.54	4.311%	$76.7103	$76.71	$76.70	$76.70
Purchase #2	$173.31	13.503%	$196.712	$196.71	$196.70	$196.70
Purchase #3	$189.44	5.744%	$200.3214	$200.32	$200.30	$200.30
Purchase #4	$187.76	4.479%	$196.1698	$196.17	$196.15	$196.20
Purchase #5	$187.41	13.321%	$212.3749	$212.37	$212.35	$212.40
Purchase #6	$149.86	9.865%	$164.6437	$164.64	$164.65	$164.60
Purchase #7	$39.42	3.480%	$40.7918	$40.79	$40.80	$40.80
7 purchase totals =	$1,000.74		$1,087.7239	$1,087.71	$1,087.65	$1,087.70