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	$87.84	5.867%	$92.9936	$92.99	$93.00	$93.00
Purchase #2	$184.91	11.871%	$206.8607	$206.86	$206.85	$206.90
Purchase #3	$162.76	12.385%	$182.9178	$182.92	$182.90	$182.90
Purchase #4	$71.39	9.837%	$78.4126	$78.41	$78.40	$78.40
Purchase #5	$130.86	10.554%	$144.671	$144.67	$144.65	$144.70
Purchase #6	$164.95	5.229%	$173.5752	$173.58	$173.60	$173.60
Purchase #7	$139.69	4.362%	$145.7833	$145.78	$145.80	$145.80
7 purchase totals =	$942.40		$1,025.2142	$1,025.21	$1,025.20	$1,025.30