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	$79.87	10.197%	$88.0143	$88.01	$88.00	$88.00
Purchase #2	$179.43	11.863%	$200.7158	$200.72	$200.70	$200.70
Purchase #3	$134.33	9.477%	$147.0605	$147.06	$147.05	$147.10
Purchase #4	$56.58	4.846%	$59.3219	$59.32	$59.30	$59.30
Purchase #5	$195.52	6.660%	$208.5416	$208.54	$208.55	$208.50
Purchase #6	$222.39	8.554%	$241.4132	$241.41	$241.40	$241.40
Purchase #7	$185.83	5.456%	$195.9689	$195.97	$195.95	$196.00
7 purchase totals =	$1,053.95		$1,141.0362	$1,141.03	$1,140.95	$1,141.00