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	$196.38	13.824%	$223.5276	$223.53	$223.55	$223.50
Purchase #2	$55.76	13.472%	$63.272	$63.27	$63.25	$63.30
Purchase #3	$44.58	3.201%	$46.007	$46.01	$46.00	$46.00
Purchase #4	$59.67	5.326%	$62.848	$62.85	$62.85	$62.80
Purchase #5	$141.95	10.235%	$156.4786	$156.48	$156.50	$156.50
Purchase #6	$249.79	3.224%	$257.8432	$257.84	$257.85	$257.80
Purchase #7	$89.54	11.500%	$99.8371	$99.84	$99.85	$99.80
7 purchase totals =	$837.67		$909.8135	$909.82	$909.85	$909.70