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	$179.54	10.150%	$197.7633	$197.76	$197.75	$197.80
Purchase #2	$97.68	8.226%	$105.7152	$105.72	$105.70	$105.70
Purchase #3	$99.57	6.356%	$105.8987	$105.90	$105.90	$105.90
Purchase #4	$122.42	3.773%	$127.0389	$127.04	$127.05	$127.00
Purchase #5	$65.49	8.811%	$71.2603	$71.26	$71.25	$71.30
Purchase #6	$71.51	12.645%	$80.5524	$80.55	$80.55	$80.60
Purchase #7	$41.64	10.373%	$45.9593	$45.96	$45.95	$46.00
7 purchase totals =	$677.85		$734.1881	$734.19	$734.15	$734.30