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	$143.89	5.176%	$151.3377	$151.34	$151.35	$151.30
Purchase #2	$155.52	7.411%	$167.0456	$167.05	$167.05	$167.00
Purchase #3	$156.31	5.395%	$164.7429	$164.74	$164.75	$164.70
Purchase #4	$66.82	6.352%	$71.0644	$71.06	$71.05	$71.10
Purchase #5	$138.56	8.498%	$150.3348	$150.33	$150.35	$150.30
Purchase #6	$46.44	10.680%	$51.3998	$51.40	$51.40	$51.40
Purchase #7	$233.76	9.447%	$255.8433	$255.84	$255.85	$255.80
7 purchase totals =	$941.30		$1,011.7685	$1,011.76	$1,011.80	$1,011.60