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	$59.89	4.803%	$62.7665	$62.77	$62.75	$62.80
Purchase #2	$134.76	3.289%	$139.1923	$139.19	$139.20	$139.20
Purchase #3	$191.53	4.211%	$199.5953	$199.60	$199.60	$199.60
Purchase #4	$122.69	9.719%	$134.6142	$134.61	$134.60	$134.60
Purchase #5	$147.32	7.521%	$158.3999	$158.40	$158.40	$158.40
Purchase #6	$106.72	7.201%	$114.4049	$114.40	$114.40	$114.40
Purchase #7	$179.38	6.259%	$190.6074	$190.61	$190.60	$190.60
7 purchase totals =	$942.29		$999.5805	$999.58	$999.55	$999.60