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	$238.76	7.334%	$256.2707	$256.27	$256.25	$256.30
Purchase #2	$65.67	8.698%	$71.382	$71.38	$71.40	$71.40
Purchase #3	$122.41	8.869%	$133.2665	$133.27	$133.25	$133.30
Purchase #4	$41.78	6.183%	$44.3633	$44.36	$44.35	$44.40
Purchase #5	$41.78	8.120%	$45.1725	$45.17	$45.15	$45.20
Purchase #6	$59.59	8.481%	$64.6438	$64.64	$64.65	$64.60
Purchase #7	$159.90	5.297%	$168.3699	$168.37	$168.35	$168.40
7 purchase totals =	$729.89		$783.4687	$783.46	$783.40	$783.60