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	$142.74	10.730%	$158.056	$158.06	$158.05	$158.10
Purchase #2	$150.65	3.481%	$155.8941	$155.89	$155.90	$155.90
Purchase #3	$59.95	8.236%	$64.8875	$64.89	$64.90	$64.90
Purchase #4	$144.82	10.601%	$160.1724	$160.17	$160.15	$160.20
Purchase #5	$129.82	10.607%	$143.59	$143.59	$143.60	$143.60
Purchase #6	$168.39	8.800%	$183.2083	$183.21	$183.20	$183.20
Purchase #7	$185.60	3.706%	$192.4783	$192.48	$192.50	$192.50
7 purchase totals =	$981.97		$1,058.2866	$1,058.29	$1,058.30	$1,058.40