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	$62.52	4.659%	$65.4328	$65.43	$65.45	$65.40
Purchase #2	$181.54	12.383%	$204.0201	$204.02	$204.00	$204.00
Purchase #3	$140.33	5.295%	$147.7605	$147.76	$147.75	$147.80
Purchase #4	$81.86	5.505%	$86.3664	$86.37	$86.35	$86.40
Purchase #5	$67.88	6.452%	$72.2596	$72.26	$72.25	$72.30
Purchase #6	$78.48	4.731%	$82.1929	$82.19	$82.20	$82.20
Purchase #7	$248.85	8.301%	$269.507	$269.51	$269.50	$269.50
7 purchase totals =	$861.46		$927.5393	$927.54	$927.50	$927.60