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	$149.91	4.226%	$156.2452	$156.25	$156.25	$156.20
Purchase #2	$177.77	5.678%	$187.8638	$187.86	$187.85	$187.90
Purchase #3	$92.34	7.398%	$99.1713	$99.17	$99.15	$99.20
Purchase #4	$231.83	13.394%	$262.8813	$262.88	$262.90	$262.90
Purchase #5	$241.89	9.172%	$264.0762	$264.08	$264.10	$264.10
Purchase #6	$71.84	8.353%	$77.8408	$77.84	$77.85	$77.80
Purchase #7	$58.88	8.357%	$63.8006	$63.80	$63.80	$63.80
7 purchase totals =	$1,024.46		$1,111.8792	$1,111.88	$1,111.90	$1,111.90