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	$77.96	9.705%	$85.526	$85.53	$85.55	$85.50
Purchase #2	$168.47	7.144%	$180.5055	$180.51	$180.50	$180.50
Purchase #3	$237.77	7.120%	$254.6992	$254.70	$254.70	$254.70
Purchase #4	$12.62	5.407%	$13.3024	$13.30	$13.30	$13.30
Purchase #5	$150.92	5.492%	$159.2085	$159.21	$159.20	$159.20
Purchase #6	$134.31	7.269%	$144.073	$144.07	$144.05	$144.10
Purchase #7	$100.37	4.559%	$104.9459	$104.95	$104.95	$104.90
7 purchase totals =	$882.42		$942.2605	$942.27	$942.25	$942.20