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	$152.88	9.301%	$167.0994	$167.10	$167.10	$167.10
Purchase #2	$222.96	13.583%	$253.2447	$253.24	$253.25	$253.20
Purchase #3	$89.84	13.352%	$101.8354	$101.84	$101.85	$101.80
Purchase #4	$75.69	3.772%	$78.545	$78.55	$78.55	$78.50
Purchase #5	$24.39	3.394%	$25.2178	$25.22	$25.20	$25.20
Purchase #6	$162.65	11.386%	$181.1693	$181.17	$181.15	$181.20
Purchase #7	$54.43	11.737%	$60.8184	$60.82	$60.80	$60.80
7 purchase totals =	$782.84		$867.9300	$867.94	$867.90	$867.80