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	$69.85	11.782%	$78.0797	$78.08	$78.10	$78.10
Purchase #2	$137.34	11.561%	$153.2179	$153.22	$153.20	$153.20
Purchase #3	$123.57	10.500%	$136.5449	$136.54	$136.55	$136.50
Purchase #4	$107.86	4.497%	$112.7105	$112.71	$112.70	$112.70
Purchase #5	$90.42	6.836%	$96.6011	$96.60	$96.60	$96.60
Purchase #6	$56.29	6.393%	$59.8886	$59.89	$59.90	$59.90
Purchase #7	$77.84	13.432%	$88.2955	$88.30	$88.30	$88.30
7 purchase totals =	$663.17		$725.3382	$725.34	$725.35	$725.30