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	$43.76	3.579%	$45.3262	$45.33	$45.35	$45.30
Purchase #2	$247.42	9.555%	$271.061	$271.06	$271.05	$271.10
Purchase #3	$97.60	3.337%	$100.8569	$100.86	$100.85	$100.90
Purchase #4	$87.74	12.454%	$98.6671	$98.67	$98.65	$98.70
Purchase #5	$27.33	13.590%	$31.0441	$31.04	$31.05	$31.00
Purchase #6	$105.36	7.609%	$113.3768	$113.38	$113.40	$113.40
Purchase #7	$71.51	4.220%	$74.5277	$74.53	$74.55	$74.50
7 purchase totals =	$680.72		$734.8598	$734.87	$734.90	$734.90