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	$114.25	11.256%	$127.11	$127.11	$127.10	$127.10
Purchase #2	$190.59	3.458%	$197.1806	$197.18	$197.20	$197.20
Purchase #3	$82.32	3.825%	$85.4687	$85.47	$85.45	$85.50
Purchase #4	$45.91	12.314%	$51.5634	$51.56	$51.55	$51.60
Purchase #5	$232.65	6.278%	$247.2558	$247.26	$247.25	$247.30
Purchase #6	$85.98	4.452%	$89.8078	$89.81	$89.80	$89.80
Purchase #7	$121.69	6.366%	$129.4368	$129.44	$129.45	$129.40
7 purchase totals =	$873.39		$927.8231	$927.83	$927.80	$927.90