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	$200.72	8.711%	$218.2047	$218.20	$218.20	$218.20
Purchase #2	$167.27	5.290%	$176.1186	$176.12	$176.10	$176.10
Purchase #3	$36.77	8.646%	$39.9491	$39.95	$39.95	$39.90
Purchase #4	$29.44	10.558%	$32.5483	$32.55	$32.55	$32.50
Purchase #5	$98.52	5.361%	$103.8017	$103.80	$103.80	$103.80
Purchase #6	$78.64	13.555%	$89.2997	$89.30	$89.30	$89.30
Purchase #7	$164.77	13.226%	$186.5625	$186.56	$186.55	$186.60
7 purchase totals =	$776.13		$846.4846	$846.48	$846.45	$846.40