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	$54.71	13.863%	$62.2944	$62.29	$62.30	$62.30
Purchase #2	$43.59	5.411%	$45.9487	$45.95	$45.95	$45.90
Purchase #3	$110.54	8.408%	$119.8342	$119.83	$119.85	$119.80
Purchase #4	$193.97	6.154%	$205.9069	$205.91	$205.90	$205.90
Purchase #5	$166.29	5.476%	$175.396	$175.40	$175.40	$175.40
Purchase #6	$184.77	3.595%	$191.4125	$191.41	$191.40	$191.40
Purchase #7	$6.77	9.806%	$7.4339	$7.43	$7.45	$7.40
7 purchase totals =	$760.64		$808.2266	$808.22	$808.25	$808.10