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	$110.40	3.620%	$114.3965	$114.40	$114.40	$114.40
Purchase #2	$190.45	3.349%	$196.8282	$196.83	$196.85	$196.80
Purchase #3	$189.85	5.751%	$200.7683	$200.77	$200.75	$200.80
Purchase #4	$99.94	5.822%	$105.7585	$105.76	$105.75	$105.80
Purchase #5	$182.95	11.177%	$203.3983	$203.40	$203.40	$203.40
Purchase #6	$194.79	10.507%	$215.2566	$215.26	$215.25	$215.30
Purchase #7	$71.87	13.792%	$81.7823	$81.78	$81.80	$81.80
7 purchase totals =	$1,040.25		$1,118.1887	$1,118.20	$1,118.20	$1,118.30