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	$71.42	9.746%	$78.3806	$78.38	$78.40	$78.40
Purchase #2	$149.57	3.150%	$154.2815	$154.28	$154.30	$154.30
Purchase #3	$94.32	3.649%	$97.7617	$97.76	$97.75	$97.80
Purchase #4	$135.81	10.691%	$150.3294	$150.33	$150.35	$150.30
Purchase #5	$216.34	12.232%	$242.8027	$242.80	$242.80	$242.80
Purchase #6	$43.25	5.649%	$45.6932	$45.69	$45.70	$45.70
Purchase #7	$238.90	6.837%	$255.2336	$255.23	$255.25	$255.20
7 purchase totals =	$949.61		$1,024.4827	$1,024.47	$1,024.55	$1,024.50