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	$98.64	7.270%	$105.8111	$105.81	$105.80	$105.80
Purchase #2	$140.89	8.716%	$153.17	$153.17	$153.15	$153.20
Purchase #3	$241.75	10.850%	$267.9799	$267.98	$268.00	$268.00
Purchase #4	$51.86	5.733%	$54.8331	$54.83	$54.85	$54.80
Purchase #5	$162.29	4.375%	$169.3902	$169.39	$169.40	$169.40
Purchase #6	$84.27	6.118%	$89.4256	$89.43	$89.45	$89.40
Purchase #7	$82.69	11.662%	$92.3333	$92.33	$92.35	$92.30
7 purchase totals =	$862.39		$932.9432	$932.94	$933.00	$932.90