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	$124.31	8.268%	$134.588	$134.59	$134.60	$134.60
Purchase #2	$55.86	11.377%	$62.2152	$62.22	$62.20	$62.20
Purchase #3	$51.84	6.697%	$55.3117	$55.31	$55.30	$55.30
Purchase #4	$226.61	9.718%	$248.632	$248.63	$248.65	$248.60
Purchase #5	$96.54	9.270%	$105.4893	$105.49	$105.50	$105.50
Purchase #6	$139.61	5.569%	$147.3849	$147.38	$147.40	$147.40
Purchase #7	$115.95	13.277%	$131.3447	$131.34	$131.35	$131.30
7 purchase totals =	$810.72		$884.9658	$884.96	$885.00	$884.90