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	$149.81	8.790%	$162.9783	$162.98	$163.00	$163.00
Purchase #2	$148.83	4.428%	$155.4202	$155.42	$155.40	$155.40
Purchase #3	$146.57	12.484%	$164.8678	$164.87	$164.85	$164.90
Purchase #4	$181.70	8.172%	$196.5485	$196.55	$196.55	$196.50
Purchase #5	$102.40	13.698%	$116.4268	$116.43	$116.45	$116.40
Purchase #6	$217.39	7.753%	$234.2442	$234.24	$234.25	$234.20
Purchase #7	$59.83	7.206%	$64.1413	$64.14	$64.15	$64.10
7 purchase totals =	$1,006.53		$1,094.6271	$1,094.63	$1,094.65	$1,094.50