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	$169.94	12.425%	$191.055	$191.06	$191.05	$191.10
Purchase #2	$123.45	12.215%	$138.5294	$138.53	$138.55	$138.50
Purchase #3	$174.41	8.639%	$189.4773	$189.48	$189.50	$189.50
Purchase #4	$86.95	13.742%	$98.8987	$98.90	$98.90	$98.90
Purchase #5	$167.63	13.774%	$190.7194	$190.72	$190.70	$190.70
Purchase #6	$221.42	9.140%	$241.6578	$241.66	$241.65	$241.70
Purchase #7	$228.46	9.820%	$250.8948	$250.89	$250.90	$250.90
7 purchase totals =	$1,172.26		$1,301.2324	$1,301.24	$1,301.25	$1,301.30