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	$44.29	4.185%	$46.1435	$46.14	$46.15	$46.10
Purchase #2	$102.35	7.588%	$110.1163	$110.12	$110.10	$110.10
Purchase #3	$206.80	7.614%	$222.5458	$222.55	$222.55	$222.50
Purchase #4	$185.72	13.795%	$211.3401	$211.34	$211.35	$211.30
Purchase #5	$39.96	9.690%	$43.8321	$43.83	$43.85	$43.80
Purchase #6	$174.75	10.782%	$193.5915	$193.59	$193.60	$193.60
Purchase #7	$72.61	8.609%	$78.861	$78.86	$78.85	$78.90
7 purchase totals =	$826.48		$906.4303	$906.43	$906.45	$906.30