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	$183.25	9.841%	$201.2836	$201.28	$201.30	$201.30
Purchase #2	$89.86	13.716%	$102.1852	$102.19	$102.20	$102.20
Purchase #3	$13.65	9.380%	$14.9304	$14.93	$14.95	$14.90
Purchase #4	$45.60	3.595%	$47.2393	$47.24	$47.25	$47.20
Purchase #5	$78.58	4.718%	$82.2874	$82.29	$82.30	$82.30
Purchase #6	$29.84	10.235%	$32.8941	$32.89	$32.90	$32.90
Purchase #7	$124.55	12.315%	$139.8883	$139.89	$139.90	$139.90
7 purchase totals =	$565.33		$620.7083	$620.71	$620.80	$620.70