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	$182.78	4.523%	$191.0471	$191.05	$191.05	$191.00
Purchase #2	$182.44	9.332%	$199.4653	$199.47	$199.45	$199.50
Purchase #3	$51.32	9.633%	$56.2637	$56.26	$56.25	$56.30
Purchase #4	$165.82	11.567%	$185.0004	$185.00	$185.00	$185.00
Purchase #5	$110.98	3.119%	$114.4415	$114.44	$114.45	$114.40
Purchase #6	$55.56	7.340%	$59.6381	$59.64	$59.65	$59.60
Purchase #7	$143.60	9.706%	$157.5378	$157.54	$157.55	$157.50
7 purchase totals =	$892.50		$963.3939	$963.40	$963.40	$963.30