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	$59.34	5.820%	$62.7936	$62.79	$62.80	$62.80
Purchase #2	$150.70	6.578%	$160.613	$160.61	$160.60	$160.60
Purchase #3	$139.96	5.185%	$147.2169	$147.22	$147.20	$147.20
Purchase #4	$173.36	13.583%	$196.9075	$196.91	$196.90	$196.90
Purchase #5	$112.72	13.147%	$127.5393	$127.54	$127.55	$127.50
Purchase #6	$47.76	5.141%	$50.2153	$50.22	$50.20	$50.20
Purchase #7	$242.43	5.360%	$255.4242	$255.42	$255.40	$255.40
7 purchase totals =	$926.27		$1,000.7098	$1,000.71	$1,000.65	$1,000.60