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	$206.43	6.368%	$219.5755	$219.58	$219.60	$219.60
Purchase #2	$223.54	5.377%	$235.5597	$235.56	$235.55	$235.60
Purchase #3	$59.91	5.116%	$62.975	$62.98	$63.00	$63.00
Purchase #4	$147.94	5.618%	$156.2513	$156.25	$156.25	$156.30
Purchase #5	$91.48	11.591%	$102.0834	$102.08	$102.10	$102.10
Purchase #6	$67.83	3.680%	$70.3261	$70.33	$70.35	$70.30
Purchase #7	$66.46	7.320%	$71.3249	$71.32	$71.30	$71.30
7 purchase totals =	$863.59		$918.0959	$918.10	$918.15	$918.20