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	$107.74	3.251%	$111.2426	$111.24	$111.25	$111.20
Purchase #2	$139.78	3.360%	$144.4766	$144.48	$144.50	$144.50
Purchase #3	$198.94	12.524%	$223.8552	$223.86	$223.85	$223.90
Purchase #4	$84.68	8.150%	$91.5814	$91.58	$91.60	$91.60
Purchase #5	$130.98	8.775%	$142.4735	$142.47	$142.45	$142.50
Purchase #6	$36.36	13.624%	$41.3137	$41.31	$41.30	$41.30
Purchase #7	$121.66	7.337%	$130.5862	$130.59	$130.60	$130.60
7 purchase totals =	$820.14		$885.5292	$885.53	$885.55	$885.60