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	$74.58	10.653%	$82.525	$82.53	$82.55	$82.50
Purchase #2	$10.86	5.645%	$11.473	$11.47	$11.45	$11.50
Purchase #3	$90.38	8.477%	$98.0415	$98.04	$98.05	$98.00
Purchase #4	$174.58	4.815%	$182.986	$182.99	$183.00	$183.00
Purchase #5	$72.83	8.280%	$78.8603	$78.86	$78.85	$78.90
Purchase #6	$240.95	5.368%	$253.8842	$253.88	$253.90	$253.90
Purchase #7	$143.86	5.177%	$151.3076	$151.31	$151.30	$151.30
7 purchase totals =	$808.04		$859.0776	$859.08	$859.10	$859.10