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	$52.47	8.395%	$56.8749	$56.87	$56.85	$56.90
Purchase #2	$155.79	11.437%	$173.6077	$173.61	$173.60	$173.60
Purchase #3	$89.60	9.320%	$97.9507	$97.95	$97.95	$98.00
Purchase #4	$232.79	5.467%	$245.5166	$245.52	$245.50	$245.50
Purchase #5	$131.94	12.517%	$148.4549	$148.45	$148.45	$148.50
Purchase #6	$237.58	12.837%	$268.0781	$268.08	$268.10	$268.10
Purchase #7	$193.79	3.666%	$200.8943	$200.89	$200.90	$200.90
7 purchase totals =	$1,093.96		$1,191.3772	$1,191.37	$1,191.35	$1,191.50