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	$102.53	9.398%	$112.1658	$112.17	$112.15	$112.20
Purchase #2	$194.54	7.592%	$209.3095	$209.31	$209.30	$209.30
Purchase #3	$109.31	3.119%	$112.7194	$112.72	$112.70	$112.70
Purchase #4	$248.51	12.484%	$279.534	$279.53	$279.55	$279.50
Purchase #5	$55.35	3.432%	$57.2496	$57.25	$57.25	$57.20
Purchase #6	$226.37	8.303%	$245.1655	$245.17	$245.15	$245.20
Purchase #7	$168.81	9.473%	$184.8014	$184.80	$184.80	$184.80
7 purchase totals =	$1,105.42		$1,200.9452	$1,200.95	$1,200.90	$1,200.90