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	$81.63	7.872%	$88.0559	$88.06	$88.05	$88.10
Purchase #2	$80.92	5.575%	$85.4313	$85.43	$85.45	$85.40
Purchase #3	$34.72	12.384%	$39.0197	$39.02	$39.00	$39.00
Purchase #4	$188.82	10.390%	$208.4384	$208.44	$208.45	$208.40
Purchase #5	$33.38	6.466%	$35.5384	$35.54	$35.55	$35.50
Purchase #6	$228.74	4.263%	$238.4912	$238.49	$238.50	$238.50
Purchase #7	$88.90	10.274%	$98.0336	$98.03	$98.05	$98.00
7 purchase totals =	$737.11		$793.0085	$793.01	$793.05	$792.90